When fat is lost from the body, it is primarily converted into carbon dioxide and water. The majority of the fat—about 84% of it—leaves the body as carbon dioxide, which is exhaled through the lungs. The remaining portion becomes water, which is expelled through urine, sweat, and other bodily fluids. Thus, when losing fat, the fat cells shrink in size as their stored triglycerides are metabolized, releasing energy, carbon dioxide, and water. This process explains why breathing out fat as carbon dioxide is the main way fat leaves the body during weight loss.