Fit people might be able to lose fat and gain muscle at the same time, even if they're not eating more or less than they burn—especially over a 10-week period.

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Evidence from Studies

Supporting (1)

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Untitled Study

Contradicting (1)

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When energy balance is maintained, exercise does not induce negative fat balance in lean sedentary, obese sedentary, or lean endurance-trained individuals.

Cross-Sectional Study

Human

2009 Dec

The study looked at what happens in one day when active people exercise but eat enough to replace the calories burned. It found they didn’t burn more fat that day—so it doesn’t support the idea that you can lose fat and gain muscle without changing calorie intake.

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Similar Assertions

People used to think you couldn’t lose fat and gain muscle at the same time, but new evidence shows it’s possible if you eat right and lift weights.

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If you exercise for an hour at a moderate pace but eat back all the calories you burned, you might still store more fat over the day — even if you're fit or at a healthy weight.

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75%

If you do supervised strength training for over 10 weeks while losing weight, you can gain about 3 kg of muscle and get 25% stronger — and it’s the best way to keep or build muscle compared to other types of exercise.

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