When athletes train too much without enough recovery, their brain and body systems—like brain chemicals, hormone responses, and muscle energy production—can go out of balance, leading to overtraining syndrome.

Athletes who are overtrained might have messed-up hormone levels — like lower testosterone and higher stress hormones — which could explain why they feel so drained and don’t recover well.

If athletes don’t eat enough calories or carbs, especially during intense training, they might not recover well—and fixing that could stop them from feeling overly tired or burned out, which people often think is overtraining.

If athletes train too much and don’t eat enough, they might be misdiagnosed with overtraining when the real issue is low energy from not fueling properly.

Some athletes who are told they're just overtrained might actually be low on fuel — their bodies aren't getting enough energy or carbs — which can look like overtraining but is really a different condition called RED-S.

When male athletes are overtrained, their body’s stress and growth hormone responses to low blood sugar don’t react as strongly—this could mean their brain’s hormone control center isn’t working right.