Metabolic age

Metabolic ageis calculated by comparing one'sbasal metabolic rateto the average of one's chronologicalage group.

All the components in the body require various levels of energy to be maintained.Body fatrequires much less energy thanlean muscle,as lean muscle is much more metabolically active and therefore requires more energy expenditure to remain inhomeostasis.If comparing two individuals, with all variables being equal, the person with more leanmuscle masswill 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 withAlfred Joseph Clarkin 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,$\theta$as,

$\theta =\lambda tA^{-0.27}$

where $A$is the standard adult body weight in kilograms $t$is the time from conception $\lambda$is a dimensional coefficient that depends on the units of time being used

Taylor chose the termmetabolic ageas a nod to the work ofMax Kleiberwho used the termmetabolic time.