After a really tough bike ride, young guys can lose about half a kilo of 'lean mass' the next day if they don’t eat enough carbs to refuel — but it’s not muscle loss, it’s mostly water stuck to stored fuel in the body.

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Evidence from Studies

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Contradicting (1)

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Muscle glycogen depletion does not alter segmental extracellular and intracellular water distribution measured using bioimpedance spectroscopy.

Randomized Controlled Trial

Human

2018 Jun 1

The study found that fat-free mass went down after hard exercise without carb recovery, but the water in muscles didn’t change like we’d expect if glycogen and its water were the main reason.

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Source Study

Muscle glycogen depletion does not alter segmental extracellular and intracellular water distribution measured using bioimpedance spectroscopy.

Score: 45

DOI: 10.1152/japplphysiol.00666.2017

Similar Assertions

If young guys do really intense cycling and don't eat carbs afterward, they lose about half a kilo of lean weight in a day—mostly from lost muscle fuel and water. But if they eat carbs, their lean weight stays the same.

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87%

When young guys burn off a lot of energy during intense cycling, their muscles lose stored fuel (glycogen), but this doesn’t seem to change how water is distributed in their arms, legs, or body — at least not enough for common body scanners to detect.

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71%

After a really tough workout, young guys lose about half a liter of fluid from outside their cells within a day — and it happens whether their energy stores are low or full, so fluid changes aren't just about fuel levels.

45

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71%