Mayo Clinic Health Library

Question

Body fat: What happens to lost fat?

When you lose weight, where does the lost body fat go?

Updated: 04-28-2012

Answer

To understand the answer, it helps to remember that fat is basically stored energy. Your body converts fat to usable energy for your muscles and other tissues through a series of complex metabolic processes. This causes your fat cells to shrink.

These metabolic activities also generate heat, which helps maintain your body temperature, and waste products. These waste products — water and carbon dioxide — are excreted in your urine and sweat or exhaled from your lungs.

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