Changes in Body Composition and Energy Metabolism Introductory statements.

The variation demonstrated even in normally aging humans leads to the need to use some broad generalities when describing human physiological aging. Keep in mind that:
1- the rate of aging may be significantly influenced by events that took place during early growth and development
2- environment and lifestyle choices introduce significant variation in the start and rate of aging
3- the loss of or decline in reproductive ability seems to accelerate age-related functional loss.