This is a question I have heard many times throughout my career in the in the fitness industry, especially lately!
First, the facts. Exercising on an empty stomach is working out on what researchers call “low glycogen stores.” This simply means that your muscles are depleted of their immediate fuel sources— glycogen and glucose (sugars)—in body cells and in the bloodstream. (A recent study published in Exercise and Sports Science Reviews sheds much light on this issue.)
There is more than one way to work out on “low glycogen stores”. If you choose to work out on an empty stomach shortly after you wake up in the morning, and if this is safe and tolerable for you, that is one approach. Many of my strongest clients tell me they can’t eat before exercise because they get nauseated. The opposite is true for other clients. Most have tried both. What works best depends on the individual.
Another way work out on a low sugar supply is to do aerobic conditioning—such as our HIIT, Zumba, or Triple Fat Burn classes or other cardio exercise such as walking, jogging, or elliptical training—AFTER your strength training/resistance-based workout. This will deplete glycogen stores in the muscle temporarily so that, when you begin your cardio conditioning, you will burn fat.
If either one of these methods results in an inappropriate level of intensity for your workout or impedes your performance in any way, then working out on low glycogen stores is not for you. But there are other ways to increase fat-burning! Stay tuned…