Training on too little fuel: what the body cuts back

Read full story

Stop 1/5

The energy left for the body

EVIDENCEGUIDE 1 · REVIEW 1

READ THE ORIGINAL

A familiar pattern: a desk job by day, the gym or a run after work, and dinner cut right back to lose fat. Part of the energy a person eats is spent on training first; only what is left goes to the everyday running costs of keeping the heart beating, holding body temperature, repairing tissue and supporting reproduction. That remainder is called energy availability: intake minus the energy spent on exercise, scaled to fat-free mass (the muscle, bone and organs that remain once fat is set aside).

It is not the same thing as the more familiar energy balance. Energy balance compares everything that comes in with everything that goes out; energy availability asks how much the body still has to spend once training has been paid for. Training more, eating less, or both will shrink that remainder, and too small a remainder disturbs the body's hormonal environment.

The 2023 consensus of the International Olympic Committee (IOC) calls the chain of health and performance problems that low energy availability sets off Relative Energy Deficiency in Sport (REDs).

Educational content, not medical advice. See a clinician about your own case.