ABSTRACT
Survival early in life is more metabolically demanding and requires higher energy input. It is during these years that higher levels of physical fitness, aerobic capacity, and endurance are supported. Optimal insulin sensitivity is known to coincide with calorie restriction, while excess nutrient intake has been associated with the development of insulin resistance. Chronic diseases that occur are generally disease states of aging. They do not impact reproductive fitness and, hence, the ability to reproduce, which is consistent with the Darwinian survival of the fittest. Psychogenic stress at the adaptive lower dose along the spectrum of hormesis is considered controllable and as having the resilience or capacity to activate behavior to meet the challenge. FOXO transcription factors play a critical role in enhancing the health span of mammals by protecting against cell stressors such as energy stress, that is reduced energy availability, and oxidative stress.
