Which person is likely to have the fastest metabolism? and which is the likely to have the slowest?
a) 15 year old boy
b) 15 year old girl
c) 65 year old man
d) 65 year old woman

The 15 year old boy has the fastest metabolism, while the 65 year old woman has the slowest metabolism.

Explanation:

Metabolism is faster in younger people. As we age, this metabolism gradually "slows down". The "slowing down" of metabolism occurs by some combined factors. There is a natural process of hormonal changes, including a decrease in the production of GH and testosterone. With the drop in the level of these substances, the body tends to lose muscle mass - a process known as sarcopenia -. Muscles are totally linked to our energy consumption, as the body spends a lot of energy to maintain them. For this reason, we can conclude that 15 year olds have a much faster metabolism than 65 year olds.

In addition, men's metabolism tends to be faster than women's metabolism. In women, metabolism is slower because they have more fat mass. Routine physical exercise is a solution to speed up metabolism, but men will always have the advantage (considering a healthy man).