When fat is broken down and “burned” in your body, it’s done so through the process of lipolysis and beta-oxidation. These reactions occur in what might be considered your body’s “fat-burning department,” the mitochondria. Because they burn your body’s best source of fuel, the mitochondria are the energy warehouses of the cells.

The process is cyclical. Two carbon atoms are removed from long fatty acid chains, helping form a molecule known as acetyl-CoA. This molecule will enter the Citric Acid Cycle to produce energy in the form of ATP. This process uses an identical pathway for glucose molecules when they are used for energy rather than being stored as fat.

Mitochondria “feed” energy to your muscles by converting food to ATP energy using the same process you just read about. Fat loss happens when fatty acids are removed from their storage, where you don’t want it, and given to mitochondria to be oxidized and burned for their energy.

Needless to say, mitochondria are very important. The good news is that you can actually increase not only the effectiveness of these mitochondria, but their number. You accomplish this through exercise. (Of course, maybe you wouldn’t consider that good news, depending on how you feel about exercise). Ultimately, the more you exercise, the more efficient and effective your body will be at burning fat.

If you had access to money-printing machines, you’d want as many of them as possible. So it is with burning fat: the more mitochondria you have, the more efficient they are, and the better off you’ll be. By increasing the number of mitochondria you increase “mitochondrial density.” This density allows the mitochondria to do a better, more efficient job at changing over the fat into ATP so you can get lean. Your body will burn fat more efficiently and you’ll use your energy for muscles rather than storage.

The question, then, is how do you create more mitochondria—a process known as Mitochondrial biogenesis—and increase their density as well?

The more difficult and consistent your training is, the more your body will need to create mitochondria.