How does the body burn fat?
Quick Answer
The body breaks stored fat into fatty acids and glycerol and burns them for energy, releasing most of the mass as carbon dioxide you breathe out.
The Full Story
Fat is stored in fat cells as triglycerides. When the body needs more energy than it is getting from food, hormones trigger lipolysis, splitting triglycerides into fatty acids and glycerol, which travel in the blood to muscles and organs. There they are broken down in mitochondria to release energy. A 2014 study in the BMJ calculated that about 84 percent of the mass of burned fat leaves the body as carbon dioxide through the lungs, and the remaining 16 percent as water. Roughly 7,700 kilocalories of energy deficit are needed to lose one kilogram of body fat, and fat cells shrink rather than disappear.
Key Facts
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Suggested video title for this topic:
"How Does the Body Burn Fat — Where Does the Fat Actually Go"