![Amandines de Provence, poster by Leonetto Cappiello, 1900](https://upload.wikimedia.org/wikipedia/commons/2/29/Amandines_de_Provence%2C_poster_by_Leonetto_Cappiello%2C_1900.jpg)
Eating (also known as consuming) is the
ingestion
Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in a substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms in ...
of
food, typically to provide a
heterotroph
A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
ic
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
with
energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...
and to allow for
growth. Animals and other heterotrophs must eat in order to survive —
carnivore
A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other s ...
s eat other animals,
herbivores eat plants,
omnivores consume a mixture of both plant and animal matter, and
detritivores
Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...
eat
detritus. Fungi digest organic matter outside their bodies as opposed to animals that digest their food inside their bodies. For humans, eating is an
activity of daily living. Some individuals may limit their amount of nutritional intake. This may be a result of a lifestyle choice, due to
hunger
In politics, humanitarian aid, and the social sciences, hunger is defined as a condition in which a person does not have the physical or financial capability to eat sufficient food to meet basic Human nutrition, nutritional needs for a sustaine ...
or
famine
A famine is a widespread scarcity of food, caused by several factors including war, natural disasters, crop failure, population imbalance, widespread poverty, an economic catastrophe or government policies. This phenomenon is usually accompani ...
, as part of a
diet
Diet may refer to:
Food
* Diet (nutrition), the sum of the food consumed by an organism or group
* Dieting, the deliberate selection of food to control body weight or nutrient intake
** Diet food, foods that aid in creating a diet for weight loss ...
or as religious fasting.
Eating practices among humans
![Japanese Gothic lolita](https://upload.wikimedia.org/wikipedia/commons/a/ad/Japanese_Gothic_lolita.jpg)
Many homes have a large kitchen area devoted to preparation of meals and food, and may have a
dining room,
dining hall
A cafeteria, sometimes called a canteen outside the U.S., is a type of food service location in which there is little or no waiting staff table service, whether a restaurant or within an institution such as a large office building or schoo ...
, or another designated area for eating.
Most societies also have
restaurants,
food courts, and
food vendors so that people may eat when away from home, when lacking time to prepare food, or as a social occasion.
[John Raulston Saul (1995), "The Doubter's Companion", 155] At their highest level of sophistication, these places become "theatrical spectacles of
global cosmopolitanism Global Cosmopolitans refers to "a talented population of highly educated multilingual people that have lived, worked and studied for extensive periods in different cultures. While their international identities have diverse starting points and exper ...
and
myth."
[David Grazian (2008), "On the Make: The Hustle of Urban Nightlife", 32] At
picnics,
potluck
A potluck is a communal gathering where each guest or group contributes a different, often homemade, dish of food to be shared.
Other names for a "potluck" include: potluck dinner, pitch-in, shared lunch, spread, faith supper, carry-in dinner ...
s, and
food festival
A food festival is a festival, that uses food, often produce, as its central theme. These festivals have always been a means of uniting communities through celebrations of harvests and giving thanks for a plentiful growing season.
History
Food ...
s, eating is in fact the primary purpose of a social gathering. At many social events, food and beverages are made available to attendees.
People usually have two or three
meal
A meal is an eating occasion that takes place at a certain time and includes consumption of food. The names used for specific meals in English vary, depending on the speaker's culture, the time of day, or the size of the meal.
Although they c ...
s a day.
Snacks of smaller amounts may be consumed between meals. Doctors in the UK recommend three meals a day (with between 400–600
kcal
The calorie is a unit of energy. For historical reasons, two main definitions of "calorie" are in wide use. The large calorie, food calorie, or kilogram calorie was originally defined as the amount of heat needed to raise the temperature of o ...
per meal),
with four to six hours between.
Having three well-balanced meals (described as: half of the plate with vegetables, 1/4 protein food as meat,
..and 1/4 carbohydrates as pasta, rice)
will then amount to some 1800–2000 kcal, which is the average requirement for a regular person.
In jurisdictions under
Sharia law, it may be proscribed for
Muslim adults during the daylight hours of
Ramadan.
[Sharia and Social Engineering: p 143, R. Michael Feener - 2013][FOOD & EATING IN MEDIEVAL EUROPE - Page 73, Joel T. Rosenthal - 1998][Conscious Eating: Second Edition - Page 9, Gabriel Cousens, M.D. - 2009]
Development in humans
![Ethiopian food](https://upload.wikimedia.org/wikipedia/commons/b/b2/Ethiopian_food.jpg)
Newborn babies do not eat adult foods. They survive solely on breast milk or formula.
Small amounts of pureed food are sometimes fed to young infants as young as two or three months old, but most infants do not eat adult food until they are between six and eight months old. Young babies eat pureed
baby food
Baby food is any soft easily consumed food other than breastmilk or infant formula that is made specifically for human babies between four and six months and two years old. The food comes in many varieties and flavors that are purchased ready- ...
s because they have few teeth and immature digestive systems. Between 8 and 12 months of age, the digestive system improves, and many babies begin eating finger foods. Their diet is still limited, however, because most babies lack molars or canines at this age, and often have a limited number of incisors. By 18 months, babies often have enough teeth and a sufficiently mature digestive system to eat the same foods as adults. Learning to eat is a messy process for children, and children often do not master neatness or eating etiquette until they are five or six years old.
Eating positions
Eating positions vary according to the different regions of the world, as culture influences the way people eat their meals.
For example, most of the Middle Eastern countries, eating while sitting on the floor is most common, and it is believed to be healthier than eating while sitting to a table.
Eating in a reclining position was favored by the
Ancient Greeks
Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cult ...
at a celebration they called a
symposium, and this custom was adopted by the
Ancient Romans
In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 ...
.
Ancient Hebrews also adopted this posture for traditional celebrations of
Passover
Passover, also called Pesach (; ), is a major Jewish holiday that celebrates the Biblical story of the Israelites escape from slavery in Egypt, which occurs on the 15th day of the Hebrew month of Nisan, the first month of Aviv, or spring. ...
.
Compulsive overeating
Compulsive overeating, or emotional eating, is "the tendency to eat in response to negative emotions".
Empirical studies have indicated that anxiety leads to decreased food consumption in people with normal weight and increased food consumption in the obese.
Many laboratory studies showed that overweight individuals are more emotionally reactive and are more likely to overeat when distressed than people of normal weight. Furthermore, it was consistently found that obese individuals experience negative emotions more frequently and more intensively than do normal weight persons.
The naturalistic study by Lowe and Fisher compared the emotional reactivity and emotional eating of normal and overweight female college students. The study confirmed the tendency of obese individuals to overeat, but these findings applied only to snacks, not to meals. That means that obese individuals did not tend to eat more while having meals; rather, the amount of snacks they ate between meals was greater. One possible explanation that Lowe and Fisher suggest is obese individuals often eat their meals with others and do not eat more than average due to the reduction of distress because of the presence of other people. Another possible explanation would be that obese individuals do not eat more than the others while having meals due to social desirability. Conversely, snacks are usually eaten alone.
Hunger and satiety
There are many physiological mechanisms that control starting and stopping a meal. The control of food intake is a physiologically complex, motivated behavioral system. Hormones such as
cholecystokinin
Cholecystokinin (CCK or CCK-PZ; from Greek ''chole'', "bile"; ''cysto'', "sac"; ''kinin'', "move"; hence, ''move the bile-sac (gallbladder)'') is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat an ...
,
bombesin
Bombesin is a 14-amino acid peptide originally isolated from the skin of the European fire-bellied toad (''Bombina bombina'')
by Vittorio Erspamer ''et al.'' and named after its source. NIHMSID 45053. It has two known homologs in mammals called ...
,
neurotensin
Neurotensin is a 13 amino acid neuropeptide that is implicated in the regulation of luteinizing hormone and prolactin release and has significant interaction with the dopaminergic system. Neurotensin was first isolated from extracts of bovine ...
,
anorectin,
calcitonin
Calcitonin is a 32 amino acid peptide hormone secreted by parafollicular cells (also known as C cells) of the thyroid (or endostyle) in humans and other chordates. in the ultimopharyngeal body. It acts to reduce blood calcium (Ca2+), opposing th ...
,
enterostatin
Enterostatin is a pentapeptide derived from a proenzyme in the gastrointestinal tract called procolipase. It reduces food intake, in particular fat intake, when given peripherally or into the brain.
Function
Enterostatin is created in the intes ...
,
leptin and
corticotropin-releasing hormone
Corticotropin-releasing hormone (CRH) (also known as corticotropin-releasing factor (CRF) or corticoliberin; corticotropin may also be spelled corticotrophin) is a peptide hormone involved in stress responses. It is a releasing hormone that bel ...
have all been shown to suppress food intake.
[Geiselman, P.J. (1996). Control of food intake. A physiologically complex, motivated behavioral system. Endocrinol Metab Clin North Am. 1996 Dec;25(4):815-29.]
Initiation
![German Shepherd puppy eating out of a human hand](https://upload.wikimedia.org/wikipedia/commons/b/b5/German_Shepherd_puppy_eating_out_of_a_human_hand.jpg)
There are numerous signals given off that initiate
hunger
In politics, humanitarian aid, and the social sciences, hunger is defined as a condition in which a person does not have the physical or financial capability to eat sufficient food to meet basic Human nutrition, nutritional needs for a sustaine ...
. There are environmental signals, signals from the
gastrointestinal system
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
, and
metabolic signals that trigger hunger. The environmental signals come from the body's
senses
A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system rec ...
. The feeling of hunger could be triggered by the smell and thought of food, the sight of a plate, or hearing someone talk about food.
The signals from the stomach are initiated by the release of the
peptide hormone
Peptide hormones or protein hormones are hormones whose molecules are peptide, or proteins, respectively. The latter have longer amino acid chain lengths than the former. These hormones have an effect on the endocrine system of animals, including h ...
ghrelin. Ghrelin is a hormone that increases appetite by signaling to the brain that a person is hungry.
Environmental signals and ghrelin are not the only signals that initiate hunger, there are other metabolic signals as well. As time passes between meals, the body starts to take nutrients from long-term reservoirs.
When the glucose levels of cells drop (glucoprivation), the body starts to produce the feeling of hunger. The body also stimulates eating by detecting a drop in cellular lipid levels (lipoprivation).
Both the brain and the liver monitor the levels of metabolic fuels. The brain checks for glucoprivation on its side of the blood–brain barrier (since glucose is its fuel), while the liver monitors the rest of the body for both lipoprivation and glucoprivation.
Termination
There are short-term signals of satiety that arise from the head, the stomach, the intestines, and the liver. The long-term signals of satiety come from
adipose tissue
Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular ...
.
The taste and odor of food can contribute to short-term satiety, allowing the body to learn when to stop eating. The stomach contains receptors to allow us to know when we are full. The intestines also contain receptors that send satiety signals to the brain. The hormone
cholecystokinin
Cholecystokinin (CCK or CCK-PZ; from Greek ''chole'', "bile"; ''cysto'', "sac"; ''kinin'', "move"; hence, ''move the bile-sac (gallbladder)'') is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat an ...
is secreted by the
duodenum, and it controls the rate at which the stomach is emptied.
This hormone is thought to be a satiety signal to the brain.
Peptide YY
Peptide YY (PYY) also known as peptide tyrosine tyrosine is a peptide that in humans is encoded by the gene. Peptide YY is a short (36-amino acid) peptide released from cells in the ileum and colon in response to feeding. In the blood, gut, a ...
3-36 is a hormone released by the
small intestine and it is also used as a satiety signal to the brain.
Insulin also serves as a satiety signal to the brain. The brain detects
insulin in the blood, which indicates that nutrients are being absorbed by cells and a person is getting full. Long-term satiety comes from the fat stored in adipose tissue. Adipose tissue secretes the hormone
leptin, and leptin suppresses appetite. Long-term satiety signals from adipose tissue regulates short-term satiety signals.
Role of the brain
The
brain stem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is co ...
can control food intake, because it contains neural circuits that detect hunger and satiety signals from other parts of the body.
The brain stem's involvement of food intake has been researched using rats. Rats that have had the motor neurons in the brain stem disconnected from the neural circuits of the cerebral hemispheres (decerebration), are unable to approach and eat food.
Instead they have to obtain their food in a liquid form. This research shows that the brain stem does in fact play a role in eating.
There are two peptides in the
hypothalamus
The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...
that produce hunger,
melanin concentrating hormone
Melanin-concentrating hormone (MCH), also known as pro-melanin stimulating hormone (PMCH), is a cyclic 19-amino acid orexigenic hypothalamic peptide originally isolated from the pituitary gland of teleost fish, where it controls skin pigmentation ...
(MCH) and
orexin
Orexin (), also known as hypocretin, is a neuropeptide that regulates arousal, wakefulness, and appetite. The most common form of narcolepsy, type 1, in which the individual experiences brief losses of muscle tone ("drop attacks" or cataplexy) ...
. MCH plays a bigger role in producing hunger. In mice, MCH stimulates feeding and a mutation causing the overproduction of MCH led to overeating and obesity.
Orexin plays a greater role in controlling the relationship between eating and sleeping. Other peptides in the hypothalamus that induce eating are neuropeptide Y (NPY) and agouti-related protein (AGRP).
Satiety in the hypothalamus is stimulated by leptin. Leptin targets the receptors on the arcuate nucleus and suppresses the secretion of MCH and orexin. The arcuate nucleus also contains two more peptides that suppress hunger. The first one is
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 ...
(CART), the second is α-MSH (α-melanocyte-stimulating hormone).
Disorders
Physiologically, eating is generally triggered by
hunger
In politics, humanitarian aid, and the social sciences, hunger is defined as a condition in which a person does not have the physical or financial capability to eat sufficient food to meet basic Human nutrition, nutritional needs for a sustaine ...
, but there are numerous physical and psychological conditions that can affect
appetite and disrupt normal eating patterns. These include
depression, food
allergies
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermat ...
, ingestion of certain chemicals,
bulimia
Bulimia nervosa, also known as simply bulimia, is an eating disorder characterized by binge eating followed by purging or fasting, and excessive concern with body shape and weight. The aim of this activity is to expel the body of calories eaten ...
,
anorexia nervosa
Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gr ...
,
pituitary gland
In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The ...
malfunction and other
endocrine problems, and numerous other
illness
A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
es and
eating disorders.
A chronic lack of nutritious food can cause various illnesses, and will eventually lead to
starvation. When this happens in a locality on a massive scale, it is considered a
famine
A famine is a widespread scarcity of food, caused by several factors including war, natural disasters, crop failure, population imbalance, widespread poverty, an economic catastrophe or government policies. This phenomenon is usually accompani ...
.
If eating and
drinking
Drinking is the act of ingesting water or other liquids into the body through the mouth, proboscis, or elsewhere. Humans drink by swallowing, completed by peristalsis in the esophagus. The physiological processes of drinking vary widely am ...
is not possible, as is often the case when recovering from
surgery, alternatives are
enteral
Enteral administration is food or drug administration via the human gastrointestinal tract. This contrasts with parenteral nutrition or drug administration (Greek ''para'', "besides" + ''enteros''), which occurs from routes outside the GI tract, ...
nutrition and
parenteral nutrition
Parenteral nutrition (PN) is the feeding of nutritional products to a person intravenously, bypassing the usual process of eating and digestion. The products are made by pharmaceutical compounding companies. The person receives a nutritional mi ...
.
[Heisler, Jennifer. "Surgery." About.com. N.p., May–June 2010. Web. 13 Mar. 2013.]
Other animals
Mammals
Birds
See also
*
Aphagia
*
Chewing
Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, th ...
*
Competitive eating
Competitive eating, or speed eating, is an activity in which participants compete against each other to eat large quantities of food, usually in a short time period. Contests are typically eight to ten minutes long, although some competitions c ...
*
Crop
A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydropon ...
*
Dietary supplement
*
Dieting
*
Dining in
Dining in is a formal military ceremony for members of a company or other unit, which includes a dinner, drinking, and other events to foster camaraderie and ''esprit de corps''.
The United States Army, the United States Navy, the United States ...
, formal military ceremony
*
Drinking
Drinking is the act of ingesting water or other liquids into the body through the mouth, proboscis, or elsewhere. Humans drink by swallowing, completed by peristalsis in the esophagus. The physiological processes of drinking vary widely am ...
*
Eat Me (disambiguation)
*
Eat This, Not That
''Eat This, Not That!'' (''ETNT'') is a media franchise owned and operated by co-author David Zinczenko. The original book series was developed from a column from ''Men's Health'' magazine written by David Zinczenko and Matt Goulding and since ...
*
Energy crop
*
Foodways
In social science, foodways are the cultural, social, and economic practices relating to the production and consumption of food. ''Foodways'' often refers to the intersection of food in culture, traditions, and history.
Definition and historical ...
*
Forced feeding
Force-feeding is the practice of feeding a human or animal against their will. The term ''gavage'' (, , ) refers to supplying a substance by means of a small plastic feeding tube passed through the nose ( nasogastric) or mouth (orogastric) into t ...
*
Muk-bang
*
Swallowing
References
External links
*
Health-EU Portal - Nutrition
{{Authority control
Physiology
Food and drink
Nutrition
Human positions
Dining