basal metabolic rate
Basal metabolic rate (BMR) is the rate of food energy, energy expenditure per unit time by endotherm, endothermic animals at rest. It is reported in energy units per unit time ranging from watt (joule/second) to ml O2/min or joule per hour per kg b ...
to the average of one's chronological age group.
All the components in the body require various levels of energy to be maintained. Body fat requires much less energy than lean muscle, as lean muscle is much more metabolically active and therefore requires more energy expenditure to remain in
homeostasis
In biology, homeostasis (British English, British also homoeostasis) Help:IPA/English, (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physics, physical, and chemistry, chemical conditions maintained by organism, living systems. Thi ...
. If comparing two individuals, with all variables being equal, the person with more lean
muscle mass
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle ...
will have a higher basal metabolic rate, and therefore, a lower metabolic age in comparison to those with the identical chronological age.
History
The research on which the concept of metabolic age is based began with
Alfred Joseph Clark
Professor Alfred Joseph Clark MC FRS FRSE (19 August 1885 – 30 July 1941) was a British pharmacologist and Professor of Pharmacology at the University College, London. He was a de-bunker of fraudulent remedies and did many early studies on ...
in 1927. Clark found that the pulse rate of different species of animal varied with body size to the power of −0.27. Other researchers went on to find that other biological rates varied to the same, or a similar, coefficient. S. Brody developed a physiological age scale in 1945. In 1961 SCS Taylor used Brody's scale as a basis for a metabolic age scale along with taking 0.27 as a standard for the calculation. Taylor thus defines metabolic age, as,
:
where
is the standard adult body weight in kilograms
is the time from conception
is a dimensional coefficient that depends on the units of time being used
Taylor chose the term ''metabolic age'' as a nod to the work of
Max Kleiber
Max Kleiber (4 January 1893 – 5 January 1976) was a Swiss agricultural biologist, born and educated in