The brain signals fat cells to release the energy packages, or fatty acid molecules, to the bloodstream. The muscles, lungs and heart pick up these fatty acids, break them apart, and use the energy stored in the bonds to execute their activities.

How does fat leave your body?

Your body must dispose of fat deposits through a series of complicated metabolic pathways. The byproducts of fat metabolism leave your body: As water, through your skin (when you sweat) and your kidneys (when you urinate). As carbon dioxide, through your lungs (when you breathe out).

What triggers fat burning?

We've all heard the term 'fat-burning', but how does it really happen in the body? Fat cells in the body release a hormone that signals to the brain that there is enough energy stored. This triggers your body to burn energy stored as fat.