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Obesity is a
medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not due to any immediate external injury. Diseases are often known to be medical ...
in which excess
body fat Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the four basic types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesod ...
has accumulated to an extent that it may have a negative effect on health. People are generally considered obese when their
body mass index Body mass index (BMI) is a value derived from the mass (Mass versus weight, weight) and height of a person. The BMI is defined as the human body weight, body mass divided by the square (algebra), square of the human height, body height, and is ...

body mass index
(BMI), a measurement obtained by dividing a person's weight by the square of the person's height—despite known
allometric Allometry is the study of the relationship of body size to shape A shape is the form of an object or its external boundary, outline, or external surface, as opposed to other properties such as color Color ( American English), or colou ...
inaccuracies—is over ; the range is defined as
overweight Being overweight or fat is having more body fat Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the four basic types of animal tissue (biology), tissue, along with epithelial tissue, muscle ...

overweight
. Some
East Asia East Asia is the eastern region of Asia, which is defined in both Geography, geographical and culture, ethno-cultural terms. The modern State (polity), states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. ...

East Asia
n countries use lower values. Obesity is a major cause of disability and is correlated with various diseases and conditions, particularly
cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped ...
s,
type 2 diabetes Type 2 diabetes (T2D), formerly known as adult-onset diabetes, is a form of diabetes Diabetes mellitus (DM), commonly known as diabetes, is a group of metabolic disorders characterized by a high blood sugar level over a prolonged period of ...
,
obstructive sleep apnea Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and is characterized by recurrent episodes of complete or partial airway obstruction, obstruction of the respiratory tract#Upper respiratory tract, upper airway lead ...
, certain types of
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumor A benign tumor is a mass of cells Cell most often refers to: * Cell (biolo ...

cancer
, and
osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease An arthropathy is a disease of a joint. Signs and symptoms Arthralgia, Joint pain is a common but non-specific sign of joint disease. Signs will depend on the specific disease, and may ...

osteoarthritis
. High BMI is a marker of risk for, but not a direct cause of, diseases caused by diet and physical activity. A reciprocal link has been found between obesity and
depression Depression may refer to: Mental health * Depression (mood), a state of low mood and aversion to activity * Mood disorders characterized by depression are commonly referred to as simply ''depression'', including: ** Dysthymia ** Major depressive ...
, with obesity increasing the risk of clinical depression and also depression leading to a higher chance of developing obesity. Obesity has individual, socioeconomic, and environmental causes. Some of the known causes are diet, physical activity,
automation Automation describes a wide range of technologies that reduce human intervention in processes. Human intervention is reduced by predetermining decision criteria, subprocess relationships, and related actions — and embodying those predetermi ...
,
urbanization Urbanization (or urbanisation) refers to the population shift from rural File:Rural landscape in Finland.jpg, A rural landscape in Lappeenranta, South Karelia, Finland. 15 July 2000. In general, a rural area or a countryside is a geographi ...
,
genetic susceptibility Public health genomics is the use of genomics information to benefit public health. This is visualized as more effective preventive care and disease treatments with better Specificity (statistics), specificity, tailored to the genetic makeup of eac ...
,
medications A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug File:Aspirine macro shot.jpg, Uncoated aspirin Tablet (pharmacy), tablets, consisting of about 90% acetylsalicylic acid, along with a ...

medications
,
mental disorder A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing In internal medici ...
s,
economic policies The economic policy of government A government is the system or group of people governing an organized community, generally a State (polity), state. In the case of its broad associative definition, government normally consists of ...
, endocrine disorders, and exposure to endocrine-disrupting chemicals. Epidemiologic studies of overweight and obesity in children and adults covering 195 countries have shown that the prevalence of obesity has steadily increased in most countries, doubling in 73 countries over the 25 years from 1980 to 2015. As of 2015, the United States and China had the largest numbers of obese adults, and China and India had the largest numbers of obese children. By 2018, 42% of Americans were obese. While a majority of obese individuals at any given time are attempting to lose weight and are often successful, research shows that maintaining that weight loss over the long term proves to be rare. The reasons for weight cycling are not fully understood but may include decreased energy expenditure combined with an increased biological urge to eat during and after caloric restriction. More studies are needed to determine if weight cycling and yo-yo dieting contribute to inflammation and disease risk in obese individuals. Obesity prevention requires a complex approach, including interventions at community, family, and individual levels. Changes to
diet Diet may refer to: Food * Diet (nutrition) In nutrition, diet is the sum of food consumed by a person or other organism. The word diet often implies the use of specific intake of nutrition for #Health, health or #Weight management, weight-mana ...
and exercising are the main treatments recommended by health professionals. Diet quality can be improved by reducing the consumption of energy-dense foods, such as those high in fat or sugars, and by increasing the intake of
dietary fiber Dietary fiber (British spelling fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzyme Digestive may refer to: Biology *Digestion Digestion is the breakdown of large insolub ...
. However, large-scale analyses have found an inverse relationship between energy density and energy cost of foods in developed nations.
Medications A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug File:Aspirine macro shot.jpg, Uncoated aspirin Tablet (pharmacy), tablets, consisting of about 90% acetylsalicylic acid, along with a ...
can be used, along with a suitable diet, to reduce appetite or decrease fat absorption. If diet, exercise, and medication are not effective, a
gastric balloon A gastric balloon, also known as an intragastric balloon (IGB) or a stomach balloon, is an inflatable medical device that is temporarily placed into the stomach to help reduce weight. It is designed to help provide weight loss when diet and exerc ...
or
surgery Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical or dental specialty that uses operative manual and instrumental techniques on a person to investigate or t ...
may be performed to reduce stomach volume or length of the intestines, leading to feeling full earlier or a reduced ability to absorb nutrients from food. Obesity is a leading worldwide, with increasing rates in adults and
children Biologically, a child (plural children) is a being between the stages of and , or between the of and puberty. The legal definition of ''child'' generally refers to a , otherwise known as a person younger than the . Children generally have ...
. In 2015, 600 million adults (12%) and 100 million children were obese in 195 countries. Obesity is more common in women than in men. Authorities view it as one of the most serious
public health Public health has been defined as "the science and art of preventing disease", prolonging life and improving quality of life Quality of life (QOL) is defined by the World Health Organization The World Health Organization (WHO) is a lis ...

public health
problems of the 21st century. Obesity is
stigmatized Social stigma is the disapproval of, or discrimination Discrimination is the act of making unjustified distinctions between people based on the groups, classes, or other categories to which they belong or are perceived to belong. People may ...
in much of the modern world (particularly in the
Western world The Western world, also known as the West, refers to various regions, nations and state (polity), states, depending on the context, most often consisting of the majority of Europe, Northern America, and Australasia.
), though it was seen as a symbol of wealth and
fertility Fertility is the capability to produce through following the onset of . The is the average number of children born by a female during her lifetime and is quantified . Fertility is addressed when there is a difficulty or an inability to repro ...
at other times in history and still is in some parts of the world. In 2013, several medical societies, including the
American Medical Association The American Medical Association (AMA), founded in 1847 and incorporated in 1897, is the largest association and lobby group Advocacy groups, also known as special interest groups, use various forms of advocacy Advocacy is an activity by a ...
and the
American Heart Association The American Heart Association (AHA) is a nonprofit organization A nonprofit organization (NPO), also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collectiv ...
, classified obesity as a
disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interactin ...
.


Classification

Obesity is a
medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not due to any immediate external injury. Diseases are often known to be medical ...
in which excess
body fat Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the four basic types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesod ...
has accumulated to the extent that it may have an adverse effect on health.WHO 2000 p.6 It is defined by
body mass index Body mass index (BMI) is a value derived from the mass (Mass versus weight, weight) and height of a person. The BMI is defined as the human body weight, body mass divided by the square (algebra), square of the human height, body height, and is ...

body mass index
(BMI) and further evaluated in terms of fat distribution via the
waist–hip ratio The waist–hip ratio or waist-to-hip ratio (WHR) is the dimensionless In dimensional analysis In engineering and science, dimensional analysis is the analysis of the relationships between different physical quantities by identifying their bas ...
and total cardiovascular risk factors. BMI is closely related to both percentage body fat and total body fat. In children, a healthy weight varies with age and sex. Obesity in children and adolescents is defined not as an absolute number but in relation to a historical normal group, such that obesity is a BMI greater than the 95th 
percentile In statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data Data (; ) are individual facts, statistics, or items of information, often numeric. In a mo ...

percentile
. The reference data on which these percentiles were based date from 1963 to 1994, and thus have not been affected by the recent increases in weight. BMI is defined as the subject's weight divided by the square of their height and is calculated as follows, :\mathrm= \frac, :where ''m'' and ''h'' are the subject's weight and height, respectively. BMI is usually expressed in kilograms of weight per metre squared of height. To convert from pounds per inch squared multiply by . The most commonly used definitions, established by the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United Nations and each other through the co-ordinating machinery of the Unit ...
(WHO) in 1997 and published in 2000, provide the values listed in the table.WHO 2000 p.9 Some modifications to the WHO definitions have been made by particular organizations. The surgical literature breaks down class II and III or only class III obesity into further categories whose exact values are still disputed. * Any BMI ≥ 35 or 40 kg/m2 is ''severe obesity''. * A BMI of ≥ 35 kg/m2 and experiencing obesity-related health conditions or ≥ 40 or 45 kg/m2 is ''morbid obesity''. * A BMI of ≥ 45 or 50 kg/m2 is ''super obesity''. As Asian populations develop negative health consequences at a lower BMI than Caucasians, some nations have redefined obesity; Japan has defined obesity as any BMI greater than 25 kg/m2 while China uses a BMI of greater than 28 kg/m2.; Originally printed as


Effects on health

Excessive body
weight In science Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe."... modern science is a discovery as well as ...
is associated with various diseases and conditions, particularly
cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped ...
s,
diabetes mellitus type 2 Type 2 diabetes (T2D), formerly known as adult-onset diabetes, is a form of diabetes Diabetes mellitus (DM), commonly known as diabetes, is a group of metabolic disorders characterized by a high blood sugar level over a prolonged period of ...
,
obstructive sleep apnea Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and is characterized by recurrent episodes of complete or partial airway obstruction, obstruction of the respiratory tract#Upper respiratory tract, upper airway lead ...
, certain types of
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumor A benign tumor is a mass of cells Cell most often refers to: * Cell (biolo ...

cancer
,
osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease An arthropathy is a disease of a joint. Signs and symptoms Arthralgia, Joint pain is a common but non-specific sign of joint disease. Signs will depend on the specific disease, and may ...

osteoarthritis
, and
asthma Asthma is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank Consolidation", M. E. Sharpe, Inc., 2002 based in Greenwich, ...

asthma
. As a result, obesity has been found to reduce
life expectancy Life expectancy is a statistical measure of the average time an organism is expected to live, based on the year of its birth, its current age, and other demographic Demography (from prefix ''demo-'' from Ancient Greek Ancien ...

life expectancy
.


Mortality

Obesity is one of the leading
preventable causes of death Preventable causes of death are causes of death related to risk factors which could have been avoided. The World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agenc ...

preventable causes of death
worldwide. A number of reviews have found that mortality risk is lowest at a BMI of 20–25 kg/m2 in non-smokers and at 24–27 kg/m2 in current smokers, with risk increasing along with changes in either direction. This appears to apply in at least four continents. In contrast, a 2013 review found that grade 1 obesity (BMI 30–34.9) was not associated with higher mortality than normal weight, and that overweight (BMI 25–29.9) was associated with "lower" mortality than was normal weight (BMI 18.5–24.9). Other evidence suggests that the association of BMI and waist circumference with mortality is U- or J-shaped, while the association between waist-to-hip ratio and
waist-to-height ratio A person's waist-to-height ratio (WHtR), also called waist-to-stature ratio (WSR), is defined as their waist circumference divided by their height, both measured in the same units. The WHtR is a measure of the distribution of body fat. Higher valu ...
with mortality is more positive. In Asians the risk of negative health effects begins to increase between 22–25 kg/m2. A BMI above 32 kg/m2 has been associated with a doubled
mortality rate Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular Statistical population, population, scaled to the size of that population, per unit of time. Mortality rate is typically e ...
among women over a 16-year period. In the United States, obesity is estimated to cause 111,909 to 365,000 deaths per year, while 1 million (7.7%) of deaths in Europe are attributed to excess weight. On average, obesity reduces life expectancy by six to seven years, a BMI of 30–35 kg/m2 reduces life expectancy by two to four years, while severe obesity (BMI ≥ 40 kg/m2) reduces life expectancy by ten years.


Morbidity

Obesity increases the risk of many physical and mental conditions. These comorbidities are most commonly shown in
metabolic syndrome Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity Abdominal obesity, also known as central obesity and truncal obesity, is a condition when excessive abdominal fat around the stomach ...
, a combination of medical disorders which includes:
diabetes mellitus type 2 Type 2 diabetes (T2D), formerly known as adult-onset diabetes, is a form of diabetes Diabetes mellitus (DM), commonly known as diabetes, is a group of metabolic disorders characterized by a high blood sugar level over a prolonged period of ...
,
high blood pressure Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank ...

high blood pressure
, high blood cholesterol, and high triglyceride levels. A study from the RAK Hospital found that obese people are at a greater risk of developing
long COVID Long COVID, also known as post-COVID-19 syndrome, post-acute sequelae of COVID-19 (PASC), or chronic COVID syndrome (CCS), is a condition characterized by long-term sequelae appearing or persisting after the typical convalescence period of coron ...
. The CDC has found that obesity is the single strongest risk factor for severe COVID-19 illness. Complications are either directly caused by obesity or indirectly related through mechanisms sharing a common cause such as a poor diet or a
sedentary lifestyle A sedentary lifestyle is a lifestyle Lifestyle often refers to: * Lifestyle (sociology), the way a person lives * ''Otium'', ancient Roman concept of a lifestyle * Style of life (german: Lebensstil), dealing with the dynamics of personality L ...
. The strength of the link between obesity and specific conditions varies. One of the strongest is the link with
type 2 diabetes Type 2 diabetes (T2D), formerly known as adult-onset diabetes, is a form of diabetes Diabetes mellitus (DM), commonly known as diabetes, is a group of metabolic disorders characterized by a high blood sugar level over a prolonged period of ...
. Excess body fat underlies 64% of cases of diabetes in men and 77% of cases in women. Health consequences fall into two broad categories: those attributable to the effects of increased fat mass (such as
osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease An arthropathy is a disease of a joint. Signs and symptoms Arthralgia, Joint pain is a common but non-specific sign of joint disease. Signs will depend on the specific disease, and may ...

osteoarthritis
,
obstructive sleep apnea Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and is characterized by recurrent episodes of complete or partial airway obstruction, obstruction of the respiratory tract#Upper respiratory tract, upper airway lead ...
, social stigmatization) and those due to the increased number of
fat cells Adipocytes, also known as lipocytes and fat cells, are the cell (biology), cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes through ad ...
(
diabetes Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorders characterized by a hyperglycemia, high blood sugar level over a prolonged period of time. Symptoms often include frequent urination, Polydipsia, increased th ...
,
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumor A benign tumor is a mass of cells Cell most often refers to: * Cell (biolo ...

cancer
,
cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped ...
,
non-alcoholic fatty liver disease Non-alcoholic fatty liver disease (NAFLD), also known as metabolic (dysfunction) associated fatty liver disease (MAFLD), is excessive build-up in the without another clear cause such as . There are two types; non-alcoholic fatty liver (NAFL) a ...
). Increases in body fat alter the body's response to insulin, potentially leading to
insulin resistance Insulin resistance (IR) is a pathological condition in which cell (biology), cells fail to respond normally to the hormone insulin. Insulin is a hormone that allows glucose to enter cells which also reduces blood glucose (blood sugar). Insulin is ...
. Increased fat also creates a proinflammatory state, and a state.


Survival paradox

Although the negative health consequences of obesity in the general population are well supported by the available evidence, health outcomes in certain subgroups seem to be improved at an increased BMI, a phenomenon known as the obesity survival paradox. The paradox was first described in 1999 in overweight and obese people undergoing
hemodialysis Hemodialysis, also spelled haemodialysis, or simply dialysis, is a process of purifying the blood of a person whose kidney The kidneys are two reddish-brown bean-shaped organs An organ is a group of tissues with similar functions. Plant ...

hemodialysis
, and has subsequently been found in those with
heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a Syndrome, set of manifestations caused by the failure of the heart's function as a pump supporting the Circulatory system, blood flow t ...
and
peripheral artery disease Peripheral artery disease (PAD) is an abnormal narrowing of arteries An artery (plural arteries) () is a blood vessel that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxyg ...
(PAD). In people with heart failure, those with a BMI between 30.0 and 34.9 had lower mortality than those with a normal weight. This has been attributed to the fact that people often lose weight as they become progressively more ill. Similar findings have been made in other types of heart disease. People with class I obesity and heart disease do not have greater rates of further heart problems than people of normal weight who also have heart disease. In people with greater degrees of obesity, however, the risk of further cardiovascular events is increased. Even after cardiac bypass surgery, no increase in mortality is seen in the overweight and obese. One study found that the improved survival could be explained by the more aggressive treatment obese people receive after a cardiac event. Another study found that if one takes into account
chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease The lungs are the primary Organ (anatomy), organs of the respiratory system in humans and many other animals including a few fish and some snails. In mammal ...
(COPD) in those with PAD, the benefit of obesity no longer exists.


Causes

The " a calorie is a calorie" model of obesity posits a combination of excessive
food energy Food energy is chemical energy Chemical energy is the energy of chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havin ...
intake and a lack of
physical activity Physical activity is defined as any voluntary bodily movement produced by skeletal muscles that requires energy expenditure.Global Recommendations on Physical Activity for Health, 2009. World Health Organization. Geneva, Switzerland. Accessed 13/07 ...
as the cause of most cases of obesity. A limited number of cases are due primarily to genetics, medical reasons, or psychiatric illness. In contrast, increasing rates of obesity at a societal level are felt to be due to an easily accessible and palatable diet, increased reliance on cars, and mechanized manufacturing. A 2006 review identified ten other possible contributors to the recent increase of obesity: (1) insufficient sleep, (2)
endocrine disruptor Endocrine disruptors, sometimes also referred to as hormonally active agents, endocrine disrupting chemicals, or endocrine disrupting compounds are chemicals that can interfere with endocrine (or hormonal A hormone (from the Greek participle ...
s (environmental
pollutant A pollutant is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. A pollutant may cause long- or short-term damage by changing the growth rate of plant or animal spec ...
s that interfere with lipid metabolism), (3) decreased variability in ambient temperature, (4) decreased rates of
smoking Smoking is a practice in which a substance is burned and the resulting smoke Smoke is a collection of airborne and es emitted when a material undergoes or , together with the quantity of air that is or otherwise mixed into the ma ...

smoking
, because smoking suppresses appetite, (5) increased use of medications that can cause weight gain (e.g.,
atypical antipsychotics The atypical antipsychotics (AAP), also known as second generation antipsychotics (SGAs) and serotonin–dopamine antagonists (SDAs), are a group of antipsychotic drugs (antipsychotic drugs in general are also known as major tranquilizers and neu ...
), (6) proportional increases in ethnic and age groups that tend to be heavier, (7) pregnancy at a later age (which may cause susceptibility to obesity in children), (8)
epigenetic In biology, epigenetics is the study of heritability, heritable phenotype changes that do not involve alterations in the DNA sequence. The Ancient Greek, Greek prefix ''wikt:epi-, epi-'' ( "over, outside of, around") in ''epigenetics'' implies f ...
risk factors passed on generationally, (9)
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of peta ...
for higher BMI, and (10)
assortative mating Assortative mating (also referred to as positive assortative mating or homogamy) is a mating pattern and a form of sexual selection in which individuals with similar phenotypes mating, mate with one another more frequently than would be expected ...
leading to increased concentration of obesity risk factors (this would increase the number of obese people by increasing population variance in weight). According to the Endocrine Society, there is "growing evidence suggesting that obesity is a disorder of the
energy homeostasisIn biology, energy homeostasis, or the homeostatic control of energy balance, is a biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, Greek: ὀργανι ...
system, rather than simply arising from the passive accumulation of excess weight".


Diet

1961
2001–03
Map of dietary energy availability per person per day in 1961 (left) and 2001–2003 (right) Calories per person per day (kilojoules per person per day)
A 2016 review supported excess food as the primary factor. Dietary energy supply per capita varies markedly between different regions and countries. It has also changed significantly over time. From the early 1970s to the late 1990s the average food energy available per person per day (the amount of food bought) increased in all parts of the world except Eastern Europe. The United States had the highest availability with per person in 1996. This increased further in 2003 to . During the late 1990s, Europeans had per person, in the developing areas of Asia there were per person, and in sub-Saharan Africa people had per person. Total food energy consumption has been found to be related to obesity. The widespread availability of dietary guidelines has done little to address the problems of overeating and poor dietary choice. From 1971 to 2000, obesity rates in the United States increased from 14.5% to 30.9%. During the same period, an increase occurred in the average amount of food energy consumed. For women, the average increase was per day ( in 1971 and in 2004), while for men the average increase was per day ( in 1971 and in 2004). Most of this extra food energy came from an increase in carbohydrate consumption rather than fat consumption. The primary sources of these extra carbohydrates are sweetened beverages, which now account for almost 25 percent of daily food energy in young adults in America, and potato chips. Consumption of
sweetened beverages A sweetened beverage is any beverage A drink (or beverage) is a liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, ...
such as soft drinks, fruit drinks, and iced tea is believed to be contributing to the rising rates of obesity and to an increased risk of metabolic syndrome and type 2 diabetes.
Vitamin D deficiency Vitamin D deficiency, or hypovitaminosis D is defined as a vitamin D level that is below normal. It most commonly occurs in people when they have inadequate sunlight exposure (in particular sunlight with adequate ultraviolet B rays (UVB)). Vita ...
is related to diseases associated with obesity. As societies become increasingly reliant on energy-dense, big-portions, and fast-food meals, the association between fast-food consumption and obesity becomes more concerning. In the United States, consumption of fast-food meals tripled and food energy intake from these meals quadrupled between 1977 and 1995.
Agricultural policy Agricultural policy describes a set of laws relating to domestic agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentism, sedentary human civ ...
and
techniques Technique or techniques may refer to: Music * The Techniques, a Jamaican rocksteady vocal group of the 1960s *Technique (band), a British female synth pop band in the 1990s *Technique (album), ''Technique'' (album), by New Order, 1989 *Techniques ( ...
in the United States and Europe have led to lower
food prices Food prices refer to the average price level for food across countries, regions and on a global scale. Food prices have an impact on producers and consumers of food. Price levels depend on the Food industry, food production process, including f ...
. In the United States, subsidization of corn, soy, wheat, and rice through the U.S. farm bill has made the main sources of processed food cheap compared to fruits and vegetables. Calorie count laws and
nutrition facts label The nutrition facts label (also known as the nutrition information panel, and other slight variations) is a label required on most packaged food in many countries, showing what nutrients (to limit and get enough of) are in the food. Labels are usua ...
s attempt to steer people toward making healthier food choices, including awareness of how much food energy is being consumed. Obese people consistently under-report their food consumption as compared to people of normal weight. This is supported both by tests of people carried out in a
calorimeter A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classicall ...

calorimeter
room and by direct observation.


Sedentary lifestyle

A sedentary lifestyle plays a significant role in obesity. Worldwide there has been a large shift towards less physically demanding work, and currently at least 30% of the world's population gets insufficient exercise. This is primarily due to increasing use of mechanized transportation and a greater prevalence of labor-saving technology in the home. In children, there appear to be declines in levels of physical activity due to less walking and physical education. World trends in active leisure time
physical activity Physical activity is defined as any voluntary bodily movement produced by skeletal muscles that requires energy expenditure.Global Recommendations on Physical Activity for Health, 2009. World Health Organization. Geneva, Switzerland. Accessed 13/07 ...
are less clear. The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United Nations and each other through the co-ordinating machinery of the Unit ...
indicates people worldwide are taking up less active recreational pursuits, while a study from Finland found an increase and a study from the United States found leisure-time physical activity has not changed significantly. A 2011 review of physical activity in children found that it may not be a significant contributor. In both children and adults, there is an association between television viewing time and the risk of obesity. A review found 63 of 73 studies (86%) showed an increased rate of childhood obesity with increased media exposure, with rates increasing proportionally to time spent watching television.


Genetics

Like many other medical conditions, obesity is the result of an interplay between genetic and environmental factors. Polymorphisms in various
gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...

gene
s controlling
appetite Appetite is the desire to eat Eating (also known as consuming) is the ingestion of food Food is any substance consumed to provide nutritional support for an organism In biology, an organism (from Ancient Greek, Greek: ὀργα ...
and
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities A bubble of exhaled gas in water In common usage and classical mechanics, a phys ...

metabolism
predispose to obesity when sufficient food energy is present. As of 2006, more than 41 of these sites on the human genome have been linked to the development of obesity when a favorable environment is present. People with two copies of the
FTO gene Fat mass and obesity-associated protein also known as alpha-ketoglutarate-dependent dioxygenase FTO is an enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules up ...
(fat mass and obesity associated gene) have been found on average to weigh 3–4 kg more and have a 1.67-fold greater risk of obesity compared with those without the risk
allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is one of two, or more, forms of a given gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance ...
. The differences in BMI between people that are varies depending on the population examined from 6% to 85%. Obesity is a major feature in several syndromes, such as
Prader–Willi syndrome Prader–Willi syndrome (PWS) is a genetic disorder caused by a loss of function of specific genes on chromosome 15. In newborns, symptoms include hypotonia, weak muscles, poor feeding, and slow development. Beginning in childhood, those affected ...
,
Bardet–Biedl syndrome Bardet–Biedl syndrome (BBS) is a ciliopathic human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposable thumbs, hairlessness, and intelligence allowing the use of cultur ...
,
Cohen syndrome Cohen syndrome (also known as Pepper syndrome or Cervenka syndrome) is a very rare autosomal recessive In genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jon ...
, and MOMO syndrome. (The term "non-syndromic obesity" is sometimes used to exclude these conditions.) In people with early-onset severe obesity (defined by an onset before 10 years of age and body mass index over three
standard deviation In statistics, the standard deviation is a measure of the amount of variation or statistical dispersion, dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected v ...

standard deviation
s above normal), 7% harbor a single point DNA mutation. Studies that have focused on inheritance patterns rather than on specific genes have found that 80% of the offspring of two obese parents were also obese, in contrast to less than 10% of the offspring of two parents who were of normal weight. Different people exposed to the same environment have different risks of obesity due to their underlying genetics. The
thrifty gene hypothesis The thrifty gene hypothesis, or Gianfranco's hypothesis is an attempt by geneticist James V. Neel to explain why certain populations and subpopulations in the modern day are prone to diabetes mellitus type 2. He proposed the hypothesis in 1962 to ...
postulates that, due to dietary scarcity during human evolution, people are prone to obesity. Their ability to take advantage of rare periods of abundance by storing energy as fat would be advantageous during times of varying food availability, and individuals with greater adipose reserves would be more likely to survive
famine A famine is a widespread scarcity of food Food is any substance consumed to provide nutritional support for an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual con ...

famine
. This tendency to store fat, however, would be maladaptive in societies with stable food supplies. This theory has received various criticisms, and other evolutionarily-based theories such as the drifty gene hypothesis and the thrifty phenotype hypothesis have also been proposed.


Other illnesses

Certain physical and mental illnesses and the pharmaceutical substances used to treat them can increase risk of obesity. Medical illnesses that increase obesity risk include several rare genetic syndromes (listed above) as well as some congenital or acquired conditions:
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two ...

hypothyroidism
,
Cushing's syndrome Cushing's syndrome is a collection of signs and symptoms due to prolonged exposure to glucocorticoids such as cortisol. Signs and symptoms may include hypertension, high blood pressure, abdominal obesity but with thin arms and legs, reddish str ...

Cushing's syndrome
,
growth hormone deficiency Growth hormone deficiency (GHD), or human growth hormone deficiency, is a medical condition resulting from not enough growth hormone (GH). Generally the most noticeable symptom is that an individual attains a short height. Newborns may also present ...
, and some
eating disorder An eating disorder is a mental disorder defined by abnormal eating behaviors that negatively affect a person's health, physical or mental health, mental health. Only one eating disorder can be diagnosed at a given time. Types of eating disorders ...
s such as
binge eating disorder Binge eating disorder (BED) is an eating disorder characterized by frequent and recurrent binge eating episodes with associated negative psychological and social problems, but without the compensatory behaviors common to Bulimia Nervosa, OSFED ...
and
night eating syndrome Night eating syndrome (NES) is an eating disorder, characterized by a delayed circadian rhythm, circadian pattern of food intake. Although there is some degree of comorbidity with binge eating disorder, it differs from binge eating in that the amou ...
. However, obesity is not regarded as a psychiatric disorder, and therefore is not listed in the DSM-IVR as a psychiatric illness. The risk of overweight and obesity is higher in patients with psychiatric disorders than in persons without psychiatric disorders. Certain medications may cause weight gain or changes in
body composition In physical fitness Physical fitness is a state of health and well-being Well-being, also known as ''wellness'', ''prudential value'' or ''quality of life'', refers to what is intrinsically valuable relative ''to'' someone. So the well-bei ...
; these include
insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets; it is considered to be the main Anabolism, anabolic hormone of the body. It regulates the metabolism of carbohydrates, fats and p ...

insulin
,
sulfonylureaSulfonylureas (UK: sulphonylurea) are a class of organic compounds , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbo ...

sulfonylurea
s,
thiazolidinedione The thiazolidinediones , abbreviated as TZD, also known as glitazones after the prototypical drug ciglitazone, are a class of heterocyclic compounds consisting of a five-membered C3NS ring. The term usually refers to a family of drugs used in th ...

thiazolidinedione
s,
atypical antipsychotic The atypical antipsychotics (AAP), also known as second generation antipsychotics (SGAs) and serotonin–dopamine antagonists (SDAs), are a group of antipsychotic drugs (antipsychotic drugs in general are also known as major tranquilizers and neu ...
s,
antidepressant Antidepressants are medications used to treat major depressive disorder, some anxiety disorders, some chronic pain conditions, and to help manage some addictions. Common Side effect, side-effects of antidepressants include Xerostomia, dry mouth, ...
s,
steroids , a steroid with 27 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations ...
, certain
anticonvulsant Anticonvulsants (also commonly known as antiepileptic drugs or as antiseizure drugs) are a diverse group of pharmacological Pharmacology is a branch of medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of ...
s (
phenytoin Phenytoin (PHT), sold under the brand name Dilantin among others, is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures (also known as Grand Mal seizures) and focal seizures, but not absence seizures. The intr ...
and
valproate Valproate (VPA) and its valproic acid, sodium valproate, and valproate semisodium forms are medications primarily used to treat epilepsy Epilepsy is a group of non-communicable neurological disorder A neurological disorder is any disorder ...
), , and some forms of
hormonal contraception Hormonal contraception refers to birth control methods that act on the endocrine system. Almost all methods are composed of steroid hormones, although in India one selective estrogen receptor modulator is marketed as a contraceptive. The original h ...
.


Social determinants

While genetic influences are important to understanding obesity, they cannot explain the current dramatic increase seen within specific countries or globally. Though it is accepted that energy consumption in excess of energy expenditure leads to obesity on an individual basis, the cause of the shifts in these two factors on the societal scale is much debated. There are a number of theories as to the cause but most believe it is a combination of various factors. The correlation between
social class A social class is a set of concepts in the social sciences Social science is the Branches of science, branch of science devoted to the study of society, societies and the Social relation, relationships among individuals within those soc ...
and BMI varies globally. A review in 1989 found that in developed countries women of a high social class were less likely to be obese. No significant differences were seen among men of different social classes. In the developing world, women, men, and children from high social classes had greater rates of obesity. An update of this review carried out in 2007 found the same relationships, but they were weaker. The decrease in strength of correlation was felt to be due to the effects of
globalization Globalization, or globalisation (Commonwealth English The use of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which ha ...

globalization
. Among developed countries, levels of adult obesity, and percentage of teenage children who are overweight, are correlated with
income inequality 270px, Global share of wealth by wealth group, Credit Suisse, 2021 There are wide varieties of economic inequality, most notably measured using the distribution of incomeIn economics Economics () is the social science that studies ho ...
. A similar relationship is seen among US states: more adults, even in higher social classes, are obese in more unequal states. Many explanations have been put forth for associations between BMI and social class. It is thought that in developed countries, the wealthy are able to afford more nutritious food, they are under greater social pressure to remain slim, and have more opportunities along with greater expectations for
physical fitness Physical fitness is a state of health Health, according to the World Health Organization, is "a state of complete physical, Mental health, mental and social well-being and not merely the absence of disease and infirmity".World Health Organiza ...
. In undeveloped countries the ability to afford food, high energy expenditure with physical labor, and cultural values favoring a larger body size are believed to contribute to the observed patterns. Attitudes toward body weight held by people in one's life may also play a role in obesity. A correlation in BMI changes over time has been found among friends, siblings, and spouses. Stress and perceived low social status appear to increase risk of obesity. Smoking has a significant effect on an individual's weight. Those who quit smoking gain an average of 4.4 kilograms (9.7 lb) for men and 5.0 kilograms (11.0 lb) for women over ten years. However, changing rates of smoking have had little effect on the overall rates of obesity. In the United States, the number of children a person has is related to their risk of obesity. A woman's risk increases by 7% per child, while a man's risk increases by 4% per child. This could be partly explained by the fact that having dependent children decreases physical activity in Western parents. In the developing world urbanization is playing a role in increasing rate of obesity. In China overall rates of obesity are below 5%; however, in some cities rates of obesity are greater than 20%.
Malnutrition Malnutrition is 'a state of nutrition in which a deficiency or excess (or imbalance) of energy, protein and other nutrients causes measurable adverse effect on tissue and body form (body shape, size and composition) and function and clinical ou ...
in early life is believed to play a role in the rising rates of obesity in the
developing world A developing country is a sovereign state A sovereign state is a political entity A polity is an identifiable political entity—any group of people who have a collective identity, who are organized by some form of Institutionalisation, ...
. Endocrine changes that occur during periods of malnutrition may promote the storage of fat once more food energy becomes available. Consistent with cognitive epidemiological data, numerous studies confirm that obesity is associated with cognitive deficits. Whether obesity causes cognitive deficits, or vice versa is unclear at present.


Gut bacteria

The study of the effect of infectious agents on metabolism is still in its early stages.
Gut flora Gut or guts may refer to: Anatomy * Abdomen, the region of the body below the thorax but above the pelvic region * Beer gut, slang for an obese stomach * Gastrointestinal tract, the system of digestive organs in humans and other animals * Hu ...
has been shown to differ between lean and obese people. There is an indication that gut flora can affect the metabolic potential. This apparent alteration is believed to confer a greater capacity to harvest energy contributing to obesity. Whether these differences are the direct cause or the result of obesity has yet to be determined unequivocally. The use of
antibiotics An antibiotic is a type of antimicrobial An antimicrobial is an agent that kills microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is any organic, life, living system t ...
among children has also been associated with obesity later in life. An association between
viruses A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...
and obesity has been found in humans and several different animal species. The amount that these associations may have contributed to the rising rate of obesity is yet to be determined.


Other factors

A number of reviews have found an association between short duration of sleep and obesity. Whether one causes the other is unclear. Even if shorts sleep does increase weight gain it is unclear if this is to a meaningful degree or increasing sleep would be of benefit. Certain aspects of
personality Personality is the characteristic sets of behaviors, cognitions, and emotional patterns that evolve from biological and environmental factors. While there is no generally agreed upon definition of personality, most theories focus on motivation a ...
are associated with being obese.
Neuroticism In the study of psychology Psychology is the science of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, as well as feeling and thought. It is an academic discipline o ...
,
impulsivity In psychology Psychology is the science of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, as well as feeling and thought. It is an academic discipline of immense sco ...
, and sensitivity to reward are more common in people who are obese while
conscientiousness Conscientiousness is the personality trait In psychology, trait theory (also called dispositional theory) is an approach to the study of human personality psychology, personality. Trait theorists are primarily interested in the measurement of ''t ...
and
self-control Self-control, an aspect of inhibitory control Inhibitory control, also known as response inhibition, is a cognitive process Cognition () refers to "the mental action or process of acquiring knowledge and understanding through thought, exper ...

self-control
are less common in people who are obese.
Loneliness Loneliness is an unpleasant emotional response to perceived Social isolation, isolation. Loneliness is also described as Psychological pain, social pain—a psychological mechanism which motivates individuals to seek social connections. It is ...

Loneliness
is also a risk factor.


Pathophysiology

Two distinct but related processes are considered to be involved in the development of obesity: sustained positive energy balance (energy intake exceeding energy expenditure) and the resetting of the body weight "set point" at an increased value. The second process explains why finding effective obesity treatments has been difficult. While the underlying biology of this process still remains uncertain, research is beginning to clarify the mechanisms. At a biological level, there are many possible
pathophysiological Pathophysiology ( physiopathology) – a convergence of pathology Pathology is the study of the causes and effects of disease A disease is a particular abnormal condition that negatively affects the structure or function of all ...
mechanisms involved in the development and maintenance of obesity. This field of research had been almost unapproached until the
leptin Leptin (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...

leptin
gene was discovered in 1994 by J. M. Friedman's laboratory. While leptin and
ghrelin Ghrelin (or lenomorelin, International Nonproprietary Name, INN) is a hormone produced by enteroendocrine cells of the gastrointestinal tract, especially the stomach, and is often called a "hunger hormone" because it increases food intake. Bloo ...
are produced peripherally, they control appetite through their actions on the
central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecu ...

central nervous system
. In particular, they and other appetite-related hormones act on the
hypothalamus The hypothalamus (from Ancient Greek wikt:ὑπό, ὑπό, "under", and wikt:θάλαμος, θάλαμος, "chamber") is a portion of the brain that contains a number of small Nucleus (neuroanatomy), nuclei with a variety of functions. One of ...

hypothalamus
, a region of the brain central to the regulation of food intake and energy expenditure. There are several circuits within the hypothalamus that contribute to its role in integrating appetite, the
melanocortin The melanocortins are a group of peptide hormonePeptide hormones or protein hormones are hormones whose molecules are peptides or proteins, respectively. The latter have longer amino acid chain lengths than the former. These hormones have an effect ...
pathway being the most well understood. The circuit begins with an area of the hypothalamus, the
arcuate nucleus The arcuate nucleus of the hypothalamus (also known as ARH, ARC, or infundibular nucleus) is an aggregation of neuron A neuron or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections ...
, that has outputs to the
lateral hypothalamus The lateral hypothalamus (LH), also called the lateral hypothalamic area (LHA), contains the primary orexinergic nucleus within the hypothalamus that widely projects throughout the nervous system; this system of neurons mediates an array of cognit ...
(LH) and ventromedial hypothalamus (VMH), the brain's feeding and satiety centers, respectively. The arcuate nucleus contains two distinct groups of
neuron A neuron or nerve cell is an electrically excitable cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or re ...

neuron
s. The first group coexpresses
neuropeptide Y Neuropeptide Y (NPY) is a 36 amino-acid neuropeptide that is involved in various physiological and homeostatic processes in both the central and peripheral nervous systems. NPY has been identified as the most abundant peptide present in the mam ...

neuropeptide Y
(NPY) and
agouti-related peptide Agouti-related protein (AgRP), also called agouti-related peptide, is a neuropeptide produced in the brain A brain is an organ (anatomy), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It ...
(AgRP) and has stimulatory inputs to the LH and inhibitory inputs to the VMH. The second group coexpresses
pro-opiomelanocortin Pro-opiomelanocortin (POMC) is a precursor polypeptide with 241 amino acid residues. POMC is Protein biosynthesis, synthesized in Corticotropic cell, corticotrophs of the anterior pituitary from the 267-amino-acid-long polypeptide precursor pre-pro ...
(POMC) and
cocaine- and amphetamine-regulated transcript Cocaine- and amphetamine-regulated transcript, also known as CART, is a neuropeptide protein that in humans is encoded by the ''CARTPT'' gene. CART appears to have roles in reward, feeding, and stress, and it has the functional properties of an en ...
(CART) and has stimulatory inputs to the VMH and inhibitory inputs to the LH. Consequently, NPY/AgRP neurons stimulate feeding and inhibit satiety, while POMC/CART neurons stimulate satiety and inhibit feeding. Both groups of arcuate nucleus neurons are regulated in part by leptin. Leptin inhibits the NPY/AgRP group while stimulating the POMC/CART group. Thus a deficiency in leptin signaling, either via leptin deficiency or leptin resistance, leads to overfeeding and may account for some genetic and acquired forms of obesity.


Public health

The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United Nations and each other through the co-ordinating machinery of the Unit ...
(WHO) predicts that
overweight Being overweight or fat is having more body fat Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the four basic types of animal tissue (biology), tissue, along with epithelial tissue, muscle ...

overweight
and obesity may soon replace more traditional
public health Public health has been defined as "the science and art of preventing disease", prolonging life and improving quality of life Quality of life (QOL) is defined by the World Health Organization The World Health Organization (WHO) is a lis ...

public health
concerns such as
undernutrition Malnutrition is a condition that results from eating a diet which does not supply a healthy amount of one or more nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient in ...
and
infectious diseases An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxin A toxin is a harmful substance produced within living cells ...
as the most significant cause of poor health. Obesity is a public health and policy problem because of its prevalence, costs, and health effects. The
United States Preventive Services Task Force The United States Preventive Services Task Force (USPSTF) is "an independent panel of experts in primary care and prevention that systematically reviews the Evidence-based medicine, evidence of effectiveness and develops recommendations for clinica ...
recommends screening for all adults followed by behavioral interventions in those who are obese. Public health efforts seek to understand and correct the
environmental factors A biophysical environment is a life, biotic and Abiotic component, abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environ ...
responsible for the increasing prevalence of obesity in the population. Solutions look at changing the factors that cause excess food energy consumption and inhibit physical activity. Efforts include federally reimbursed meal programs in schools, limiting direct
food marketing Food marketing brings together the food producer and the consumer A consumer is a person or a group who intends to order, orders, or uses purchased goods, products, or Service (economics), services primarily for personal, social, family, house ...
to children, and decreasing access to sugar-sweetened beverages in schools. The World Health Organization recommends the taxing of sugary drinks. When constructing urban environments, efforts have been made to increase access to parks and to develop pedestrian routes. There is low quality evidence that nutritional labelling with energy information on menus can help to reduce energy intake while dining in restaurants.


Reports

Many organizations have published reports pertaining to obesity. In 1998, the first US Federal guidelines were published, titled "Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report". In 2006, the Canadian Obesity Network, now known as Obesity Canada published the "Canadian Clinical Practice Guidelines (CPG) on the Management and Prevention of Obesity in Adults and Children". This is a comprehensive evidence-based guideline to address the management and prevention of overweight and obesity in adults and children. In 2004, the United Kingdom
Royal College of Physicians The Royal College of Physicians (RCP) is a British professional membership body dedicated to improving the practice of medicine, chiefly through the accreditation of physicians by examination. Founded by royal charter from King Henry VIII in 15 ...
, the Faculty of Public Health and the
Royal College of Paediatrics and Child Health The Royal College of Paediatrics and Child Health, often referred to as the RCPCH, is the professional body for paediatricians (doctors specialising in child health) in the United Kingdom The United Kingdom of Great Britain and Northern Ire ...
released the report "Storing up Problems", which highlighted the growing problem of obesity in the UK. The same year, the
House of Commons The House of Commons is the name for the elected lower house A lower house is one of two chambers Chambers may refer to: Places Canada: *Chambers Township, Ontario United States: *Chambers County, Alabama *Chambers, Arizona, an unincorporat ...
Health Select Committee The Health and Social Care Select Committee (abbreviated to HSC, HSCC and HSCSC) is a Departmental Parliamentary select committees of the United Kingdom, Select Committee of the British House of Commons, the lower house of the United Kingdom Parl ...
published its "most comprehensive inquiry ..ever undertaken" into the impact of obesity on health and society in the UK and possible approaches to the problem. In 2006, the
National Institute for Health and Clinical Excellence The National Institute for Health and Care Excellence (NICE) is an executive non-departmental public bodyIn the United Kingdom, non-departmental public body (NDPB) is a classification applied by the Cabinet Office, HM Treasury, Treasury, the ...

National Institute for Health and Clinical Excellence
(NICE) issued a guideline on the diagnosis and management of obesity, as well as policy implications for non-healthcare organizations such as local councils. A 2007 report produced by
Derek Wanless Sir Derek Wanless (29 September 1947 – 22 May 2012) was an England, English banker and an adviser to the Labour Party. Biography Derek Wanless was born in Newcastle upon Tyne, where he was educated at the Royal Grammar School, Newcastle, ...
for the
King's Fund The King's Fund staff at the School of Advanced Study History Day, November 2019. The King's Fund is an independent think tank A think tank, or policy institute, is a research institute A research institute, research centre, or research cente ...
warned that unless further action was taken, obesity had the capacity to cripple the
National Health Service The National Health Service (NHS) is the umbrella term for the publicly funded healthcare systems of the United Kingdom (UK). Since 1948, they have been funded out of general taxation. There are three systems which are referred to using the " ...
financially. Comprehensive approaches are being looked at to address the rising rates of obesity. The Obesity Policy Action (OPA) framework divides measure into 'upstream' policies, 'midstream' policies, 'downstream' policies. 'Upstream' policies look at changing society, 'midstream' policies try to alter individuals' behavior to prevent obesity, and 'downstream' policies try to treat currently afflicted people.


Management

The main treatment for obesity consists of
weight loss Weight loss, in the context of medicine, health, or physical fitness Physical fitness is a state of health Health, according to the World Health Organization, is "a state of complete physical, Mental health, mental and social well-bein ...
via calorie restricted
dieting Dieting is the practice of eating Eating (also known as consuming) is the ingestion Ingestion is the consumption of a substance by an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismo ...
and
physical exercise Exercise is any bodily activity that enhances or maintains physical fitness Physical fitness is a state of health Health is a state of physical, mental and social well-being Well-being, also known as ''wellness'', ''prudential valu ...
. Dieting, as part of a lifestyle change, produces sustained weight loss, despite slow weight regain over time. Although 87% of participants in the National Weight Control Registry were able to maintain 10% body weight loss for 10 years, the most appropriate dietary approach for long term weight loss maintenance is still unknown. Intensive behavioral interventions combining both dietary changes and exercise are recommended. Intermittent fasting has no additional benefit of weight loss compared to continuous energy restriction. Adherence is a more important factor in weight loss success than whatever kind of diet an individual undertakes. Several hypo-caloric diets are effective. In the short-term low carbohydrate diets appear better than low fat diets for weight loss. In the long term, however, all types of low-carbohydrate and low-fat diets appear equally beneficial. A 2014 review found that the heart disease and diabetes risks associated with different diets appear to be similar. Promotion of the Mediterranean diets among the obese may lower the risk of heart disease. Decreased intake of sweet drinks is also related to weight-loss. Success rates of long-term weight loss maintenance with lifestyle changes are low, ranging from 2–20%. Dietary and lifestyle changes are effective in limiting excessive weight gain in
pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual reproduction, single organism or, in the case of sexual repr ...

pregnancy
and improve outcomes for both the mother and the child. Intensive behavioral counseling is recommended in those who are both obese and have other risk factors for heart disease.


Medical interventions

Five medications have evidence for long-term use
orlistat Orlistat is a drug designed to treat obesity Obesity is a medical condition in which excess body fat has accumulated to an extent that it may have a negative effect on health. People are generally considered obese when their body mass in ...

orlistat
,
lorcaserin Lorcaserin, marketed under the brand name Belviq is a weight-loss drug developed by Arena Pharmaceuticals. It reduces appetite by activating a type of serotonin receptor known as the 5-HT2C receptor, 5-HT2C receptor in a region of the brain call ...

lorcaserin
,
liraglutide Liraglutide, sold under the brand name Victoza among others, is a medication A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, therapy, treat, ...

liraglutide
, phentermine–topiramate, and naltrexone–bupropion. They result in weight loss after one year ranged from 3.0 to 6.7 kg (6.6-14.8 lbs) over placebo. Orlistat, liraglutide, and naltrexone–bupropion are available in both the United States and Europe, phentermine–topiramate is available only in the United States. European regulatory authorities rejected lorcaserin and phentermine-topiramate, in part because of associations of heart valve problems with lorcaserin and more general heart and blood vessel problems with phentermine–topiramate. Lorcaserin was available in the United States and then removed from the market in 2020 due to its association with cancer. Orlistat use is associated with high rates of gastrointestinal side effects and concerns have been raised about negative effects on the kidneys. There is no information on how these drugs affect longer-term complications of obesity such as cardiovascular disease or death,however, liraglutide, when used for type 2 diabetes, does reduce cardiovascular events. The most effective treatment for obesity is
bariatric surgery Bariatric surgery (or weight loss surgery) includes a variety of procedures performed on people who are obese. Long term weight loss through standard of care procedures (Gastric bypass surgery#Variations, Roux en-Y bypass, sleeve gastrectomy, ...
. The types of procedures include laparoscopic adjustable gastric banding, , vertical-sleeve gastrectomy, and
biliopancreatic diversion Bariatric surgery (or weight loss surgery) includes a variety of procedures performed on people who are obesity, obese. Long term weight loss through Standard treatment, standard of care procedures (Gastric bypass surgery#Variations, Roux en-Y b ...

biliopancreatic diversion
. Surgery for severe obesity is associated with long-term weight loss, improvement in obesity-related conditions, and decreased overall mortality, however, improved metabolic health results from the weight loss, not the surgery. One study found a weight loss of between 14% and 25% (depending on the type of procedure performed) at 10 years, and a 29% reduction in all cause mortality when compared to standard weight loss measures. Complications occur in about 17% of cases and reoperation is needed in 7% of cases.


Epidemiology

In earlier historical periods obesity was rare, and achievable only by a small elite, although already recognised as a problem for health. But as prosperity increased in the
Early Modern period The early modern period of modern history Human history, or world history, is the narrative of Human, humanity's past. It is understood through archaeology, anthropology, genetics, and linguistics, and since the History of writing, adve ...
, it affected increasingly larger groups of the population. Prior to the 1970s, obesity was a relatively rare condition even in the wealthiest of nations, and when it did exist it tended to occur among the wealthy. Then, a confluence of events started to change the human condition. The average BMI of populations in first-world countries started to increase and, consequently, there was a rapid increase in the proportion of people overweight and obese. In 1997, the WHO formally recognized obesity as a global epidemic. As of 2008, the WHO estimates that at least 500 million adults (greater than 10%) are obese, with higher rates among women than men. The global prevalence of obesity more than doubled between 1980 and 2014. In 2014, more than 600 million adults were obese, equal to about 13 percent of the world’s adult population. The percentage of adults affected in the United States as of 2015–2016 is about 39.6% overall (37.9% of males and 41.1% of females). The rate of obesity also increases with age at least up to 50 or 60 years old and severe obesity in the United States, Australia, and Canada is increasing faster than the overall rate of obesity. The
OECD The Organisation for Economic Co-operation and Development (OECD; french: Organisation de Coopération et de Développement Économiques, OCDE) is an intergovernmental economic organisation with 38 member countries, founded in 1961 to st ...

OECD
has projected an increase in obesity rates until at least 2030, especially in the United States, Mexico and England with rates reaching 47%, 39% and 35%, respectively. Once considered a problem only of high-income countries, obesity rates are rising worldwide and affecting both the developed and developing world. These increases have been felt most dramatically in urban settings. The only remaining region of the world where obesity is not common is
sub-Saharan Africa Sub-Saharan Africa (commonly called Black Africa) is, geographically, the area of the continent of Africa that lies south of the Sahara. According to the United Nations, it consists of all list of sovereign states and dependent territories i ...

sub-Saharan Africa
.


History


Etymology

''Obesity'' is from the
Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an appa ...

Latin
''obesitas'', which means "stout, fat, or plump". ''Ēsus'' is the past participle of ''edere'' (to eat), with ''ob'' (over) added to it. ''
The Oxford English Dictionary The ''Oxford English Dictionary'' (''OED'') is the principal historical dictionary of the English language, published by Oxford University Press (OUP). It traces the historical development of the English language, providing a comprehensive re ...
'' documents its first usage in 1611 by
Randle Cotgrave Randle Cotgrave was an English lexicographer Lexicography is divided into two separate but equally important groups: * Practical lexicography is the art or craft A craft or trade is a pastime or an occupation that requires particular s ...
.


Historical attitudes

Ancient Greek medicine Ancient Greek medicine was a compilation of theories and practices that were constantly expanding through new ideologies and trials. Many components were considered in ancient Greek Ancient Greek includes the forms of the Greek language us ...
recognizes obesity as a medical disorder, and records that the Ancient Egyptians saw it in the same way.
Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ε ...

Hippocrates
wrote that "Corpulence is not only a disease itself, but the harbinger of others". The Indian surgeon
Sushruta Sushruta, or ''Suśruta'' (Sanskrit Sanskrit (, attributively , ''saṃskṛta-'', nominalization, nominally , ''saṃskṛtam'') is a classical language of South Asia belonging to the Indo-Aryan languages, Indo-Aryan branch of the Indo-Eu ...

Sushruta
(6th century BCE) related obesity to diabetes and heart disorders. He recommended physical work to help cure it and its side effects. For most of human history mankind struggled with food scarcity. Obesity has thus historically been viewed as a sign of wealth and prosperity. It was common among high officials in Europe in the
Middle Ages In the history of Europe The history of Europe concerns itself with the discovery and collection, the study, organization and presentation and the interpretation of past events and affairs of the people of Europe since the beginning of ...
and the
Renaissance The Renaissance ( , ) , from , with the same meanings. is a period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in ...

Renaissance
as well as in Ancient East Asian civilizations. In the 17th century, English medical author Tobias Venner is credited with being one of the first to refer to the term as a societal disease in a published English language book. With the onset of the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe Continental Europe or mainland Europe is the contiguous continent A continent is any of several large landmasse ...
it was realized that the military and economic might of nations were dependent on both the body size and strength of their soldiers and workers. Increasing the average body mass index from what is now considered underweight to what is now the normal range played a significant role in the development of industrialized societies. Height and weight thus both increased through the 19th century in the developed world. During the 20th century, as populations reached their genetic potential for height, weight began increasing much more than height, resulting in obesity. In the 1950s increasing wealth in the developed world decreased child mortality, but as body weight increased heart and kidney disease became more common. During this time period, insurance companies realized the connection between weight and life expectancy and increased premiums for the obese. Many cultures throughout history have viewed obesity as the result of a character flaw. The ''obesus'' or fat character in
Ancient Greek comedy Ancient Greek comedy was one of the final three principal drama Drama is the specific Mode (literature), mode of fiction Mimesis, represented in performance: a Play (theatre), play, opera, mime, ballet, etc., performed in a theatre, or on R ...
was a glutton and figure of mockery. During Christian times the food was viewed as a gateway to the sins of
sloth Sloths are a group of arboreal Neotropical xenarthran mammals, constituting the suborder Folivora. Noted for their slowness of movement, they spend most of their lives hanging upside down in the trees of the tropical rainforest File:Kop ...
and
lust Lust is a psychological force producing intense desire Desire is the emotion Emotions are biological states associated with all of the nerve systems brought on by neurophysiological changes variously associated with thoughts, feelings, b ...

lust
. In modern Western culture, excess weight is often regarded as unattractive, and obesity is commonly associated with various negative stereotypes. People of all ages can face social stigmatization, and may be targeted by bullies or shunned by their peers. Public perceptions in Western society regarding healthy body weight differ from those regarding the weight that is considered ideal  – and both have changed since the beginning of the 20th century. The weight that is viewed as an ideal has become lower since the 1920s. This is illustrated by the fact that the average height of Miss America pageant winners increased by 2% from 1922 to 1999, while their average weight decreased by 12%. On the other hand, people's views concerning healthy weight have changed in the opposite direction. In Britain, the weight at which people considered themselves to be overweight was significantly higher in 2007 than in 1999. These changes are believed to be due to increasing rates of adiposity leading to increased acceptance of extra body fat as being normal. Obesity is still seen as a sign of wealth and well-being in many parts of Africa. This has become particularly common since the
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus ''Lentivirus'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, inc ...

HIV
epidemic began.


The arts

The first sculptural representations of the human body 20,000–35,000 years ago depict obese females. Some attribute the
Venus figurines A Venus figurine is any portraying a woman, usually carved in .Fagan, Brian M., Beck, Charlotte, "Venus Figurines", ''The Oxford Companion to Archaeology'', 1996, Oxford University Press, pp. 740–741 Most have been unearthed in , but others ...
to the tendency to emphasize fertility while others feel they represent "fatness" in the people of the time. Corpulence is, however, absent in both Greek and Roman art, probably in keeping with their ideals regarding moderation. This continued through much of Christian European history, with only those of low socioeconomic status being depicted as obese. During the
Renaissance The Renaissance ( , ) , from , with the same meanings. is a period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in ...

Renaissance
some of the upper class began flaunting their large size, as can be seen in portraits of
Henry VIII of England Henry VIII (28 June 149128 January 1547) was King of England This list of kings and queens of the begins with , who initially ruled , one of the which later made up modern England. Alfred styled himself King of the from about 886, a ...
and Alessandro dal Borro.
Rubens Sir Peter Paul Rubens (; ; 28 June 1577 – 30 May 1640) was a artist and diplomat from the in the (modern-day ). He is considered the most influential artist of the tradition. Rubens's highly charged compositions reference erudite aspects ...

Rubens
(1577–1640) regularly depicted heavyset women in his pictures, from which derives the term . These women, however, still maintained the "hourglass" shape with its relationship to fertility. During the 19th century, views on obesity changed in the Western world. After centuries of obesity being synonymous with wealth and social status, slimness began to be seen as the desirable standard.


Society and culture


Economic impact

In addition to its health impacts, obesity leads to many problems including disadvantages in employmentPuhl R., Henderson K., and Brownell K. 2005 p.29 and increased business costs. These effects are felt by all levels of society from individuals, to corporations, to governments. In 2005, the medical costs attributable to obesity in the US were an estimated $190.2 billion or 20.6% of all medical expenditures, while the cost of obesity in Canada was estimated at CA$2 billion in 1997 (2.4% of total health costs). The total annual direct cost of overweight and obesity in Australia in 2005 was A$21 billion. Overweight and obese Australians also received A$35.6 billion in government subsidies. The estimate range for annual expenditures on diet products is $40 billion to $100 billion in the US alone.
The Lancet ''The Lancet'' is a weekly peer-reviewed general medical journal. It is among the world's oldest and best-known general medical journals. It was founded in 1823 by Thomas Wakley, an English surgeon who named it after the surgical instrument ca ...
Commission on Obesity in 2019 called for a global treaty—modelled on the
WHO Framework Convention on Tobacco Control The World Health Organization Framework Convention on Tobacco Control (WHO FCTC) is a treaty A treaty is a formal legally binding written agreement between actors in international law. It is usually entered into by sovereign states and inter ...

WHO Framework Convention on Tobacco Control
—committing countries to address obesity and undernutrition, explicitly excluding the food industry from policy development. They estimate the global cost of obesity $2 trillion a year, about or 2.8% of world GDP. Obesity prevention programs have been found to reduce the cost of treating obesity-related disease. However, the longer people live, the more medical costs they incur. Researchers, therefore, conclude that reducing obesity may improve the public's health, but it is unlikely to reduce overall health spending. Obesity can lead to social stigmatization and disadvantages in employment. When compared to their normal weight counterparts, obese workers on average have higher rates of absenteeism from work and take more disability leave, thus increasing costs for employers and decreasing productivity. A study examining Duke University employees found that people with a BMI over 40 kg/m2 filed twice as many
workers' compensation Workers' compensation or workers' comp (formerly workmen's compensation until the name was changed to make it gender-neutral) is a form of insurance providing wage replacement and medical benefits to employees injured in the course of employment ...
claims as those whose BMI was 18.5–24.9 kg/m2. They also had more than 12 times as many lost work days. The most common injuries in this group were due to falls and lifting, thus affecting the lower extremities, wrists or hands, and backs. The Alabama State Employees' Insurance Board approved a controversial plan to charge obese workers $25 a month for health insurance that would otherwise be free unless they take steps to lose weight and improve their health. These measures started in January 2010 and apply to those state workers whose BMI exceeds 35 kg/m2 and who fail to make improvements in their health after one year. Some research shows that obese people are less likely to be hired for a job and are less likely to be promoted. Obese people are also paid less than their non-obese counterparts for an equivalent job; obese women on average make 6% less and obese men make 3% less. Specific industries, such as the airline, healthcare and food industries, have special concerns. Due to rising rates of obesity, airlines face higher fuel costs and pressures to increase seating width. In 2000, the extra weight of obese passengers cost airlines US$275 million. The healthcare industry has had to invest in special facilities for handling severely obese patients, including special lifting equipment and bariatric ambulances. Costs for restaurants are increased by litigation accusing them of causing obesity. In 2005 the US Congress discussed legislation to prevent civil lawsuits against the food industry in relation to obesity; however, it did not become law. With the
American Medical Association The American Medical Association (AMA), founded in 1847 and incorporated in 1897, is the largest association and lobby group Advocacy groups, also known as special interest groups, use various forms of advocacy Advocacy is an activity by a ...
's 2013 classification of obesity as a chronic disease, it is thought that health insurance companies will more likely pay for obesity treatment, counseling and surgery, and the cost of research and development of fat treatment pills or gene therapy treatments should be more affordable if insurers help to subsidize their cost. The AMA classification is not legally binding, however, so health insurers still have the right to reject coverage for a treatment or procedure. In 2014, The European Court of Justice ruled that morbid obesity is a disability. The Court said that if an employee's obesity prevents him from "full and effective participation of that person in professional life on an equal basis with other workers", then it shall be considered a disability and that firing someone on such grounds is discriminatory.


Size acceptance

The principal goal of the fat acceptance movement is to decrease discrimination against people who are overweight and obese. However, some in the movement are also attempting to challenge the established relationship between obesity and negative health outcomes. A number of organizations exist that promote the acceptance of obesity. They have increased in prominence in the latter half of the 20th century. The US-based
National Association to Advance Fat Acceptance The National Association to Advance Fat Acceptance (NAAFA) is a non-profit, fat acceptance civil-rights organization in the United States dedicated to improving the quality of life for the obesity, obese. NAAFA works to eliminate discrimination b ...
(NAAFA) was formed in 1969 and describes itself as a civil rights organization dedicated to ending size discrimination. The International Size Acceptance Association (ISAA) is a
non-governmental organization A non-governmental organization, or simply an NGO, is an organization that is, generally, formed independent from government. They are typically nonprofit organization, nonprofit entities, and many of them are active in humanitarianism or the ...
(NGO) which was founded in 1997. It has more of a global orientation and describes its mission as promoting size acceptance and helping to end weight-based discrimination. These groups often argue for the recognition of obesity as a disability under the US
Americans With Disabilities Act The Americans with Disabilities Act of 1990 or ADA () is a civil rights law that prohibits discrimination based on disability. It affords similar protections against discrimination to Disability in the United States, Americans with disabilities ...
(ADA). The American legal system, however, has decided that the potential public health costs exceed the benefits of extending this anti-discrimination law to cover obesity.


Industry influence on research

In 2015, the ''New York Times'' published an article on the Global Energy Balance Network, a nonprofit founded in 2014 that advocated for people to focus on increasing exercise rather than reducing calorie intake to avoid obesity and to be healthy. The organization was founded with at least $1.5M in funding from the
Coca-Cola Company The Coca-Cola Company is an American multinational beverage corporation incorporated under Delaware Delaware ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States, bordering Maryland t ...
, and the company has provided $4M in research funding to the two founding scientists Gregory A. Hand and Steven N. Blair since 2008.


Childhood obesity

The healthy BMI range varies with the age and sex of the child. Obesity in children and adolescents is defined as a BMI greater than the 95th 
percentile In statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data Data (; ) are individual facts, statistics, or items of information, often numeric. In a mo ...

percentile
. The reference data that these percentiles are based on is from 1963 to 1994 and thus has not been affected by the recent increases in rates of obesity. Childhood obesity has reached epidemic proportions in the 21st century, with rising rates in both the developed and the developing world. Rates of obesity in Canadian boys have increased from 11% in the 1980s to over 30% in the 1990s, while during this same time period rates increased from 4 to 14% in Brazilian children. In the UK, there were 60% more obese children in 2005 compared to 1989. In the US, the percentage of overweight and obese children increased to 16% in 2008, a 300% increase over the prior 30 years. As with obesity in adults, many factors contribute to the rising rates of childhood obesity. Changing diet and decreasing physical activity are believed to be the two most important causes for the recent increase in the incidence of child obesity. Antibiotics in the first 6 months of life have been associated with excess weight at age seven to twelve years of age. Because childhood obesity often persists into adulthood and is associated with numerous chronic illnesses, children who are obese are often tested for
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank ...

hypertension
,
diabetes Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorders characterized by a hyperglycemia, high blood sugar level over a prolonged period of time. Symptoms often include frequent urination, Polydipsia, increased th ...

diabetes
,
hyperlipidemia Hyperlipidemia is abnormally elevated levels of any or all lipids (fats, cholesterol, or triglycerides) or lipoproteins in the blood. citing: and The term ''hyperlipidemia'' refers to the laboratory finding itself and is also used as an umbre ...
, and
fatty liver disease Fatty liver disease (FLD), also known as hepatic steatosis, is a condition where excess fat builds up in the liver The liver is an organ only found in vertebrates which detoxifies various metabolites, synthesizes proteins and produces bio ...
. Treatments used in children are primarily lifestyle interventions and behavioral techniques, although efforts to increase activity in children have had little success. In the United States, medications are not FDA approved for use in this age group. Multi-component behaviour change interventions that include changes to dietary and physical activity may reduce BMI in the short term in children aged 6 to 11 years, although the benefits are small and quality of evidence is low.


Other animals

Obesity in pets is common in many countries. In the United States, 23–41% of dogs are overweight, and about 5.1% are obese. The rate of obesity in cats was slightly higher at 6.4%. In Australia the rate of obesity among dogs in a veterinary setting has been found to be 7.6%. The risk of obesity in dogs is related to whether or not their owners are obese; however, there is no similar correlation between cats and their owners.


References

Informational notes Citations Bibliography * Jebb S. and Wells J. Measuring body composition in adults and children In: * Kopelman P., Caterson I. An overview of obesity management In: * * * Puhl R., Henderson K., and Brownell K. Social consequences of obesity In: * Seidell JC. Epidemiology – definition and classification of obesity In: * Further reading * * * {{Authority control Bariatrics Body shape Nutrition Wikipedia medicine articles ready to translate (full) Wikipedia neurology articles ready to translate Amphetamine