Researchers from the Garvan Institute of Medical Research recently stumbled upon what they believe is the reason why fat can clog up muscle cells and make them insulin resistant: it appears that fat molecules entering the muscle aren’t being effectively shuttled into the mitochondria—the powerhouses of the cell—to be converted into useable energy. The “gatekeeper” is a protein called CPT1, which controls the entry of fat into the mitochondria. When they engineered more of this protein in rat hind limbs, their muscles burned significantly more fat and their insulin action improved. The problem this research didn’t solve, however, is that if your muscle is using more fat, it will likely be using less blood glucose, which means that less blood sugar would get used up during a workout. Interestingly, stimulating fat use in muscles—which they’re hoping to be able to do in the future as a treatment for type 2 diabetes—is exactly what exercise training does for you anyway. In effect, then, they’re trying to come up with an “exercise” pill that will cause this change in your muscles without physical activity. In my opinion, you’re better off getting the full body benefits of doing the exercise on your own!