When you lose weight, the fat stored in your body is metabolized and leaves your body primarily as carbon dioxide and water. Here's how the process works in detail:
- Fat cells store energy in the form of triglycerides, which are molecules made up of carbon, hydrogen, and oxygen. When you create a calorie deficit by consuming fewer calories than you burn, your body breaks down these triglycerides to release energy
- The chemical process of fat metabolism uses oxygen to break the bonds in fat molecules, releasing energy for your body's functions and physical activity. This process produces two main byproducts: carbon dioxide (CO2) and water (H2O)
- The carbon dioxide is expelled from your body when you exhale through your lungs. The water is eliminated through urine, sweat, and also exhaled air. In fact, the lungs are the primary organ for fat excretion because most fat leaves the body as CO2 through breathing
- During exercise, the rate of fat metabolism and the excretion of these byproducts increase due to higher breathing and sweating rates
- Fat cells shrink in size as their stored fat is used for energy, but the number of fat cells generally remains the same. This is why maintaining weight loss requires ongoing effort; the shrunken fat cells can grow again if calorie intake exceeds expenditure
In summary, when you lose weight, fat is converted into energy, carbon dioxide, and water. The carbon dioxide is breathed out, and the water leaves your body through urine, sweat, and breath
