Low energy availability is a mismatch between an athlete’s energy intake and the energy expended in exercise. This leaves inadequate energy to support the functions required by the body to maintain optimal health and performance. Much of the previous research in this area was on female athletes, but studies now show low energy availability can significantly decrease testosterone levels (and therefore muscle-building potential), as well as affecting many other aspects of health and quality of life. The takeaway: active lifestyles require ample food input for both performance and wellbeing to prosper.