Is Cardio on an Empty Stomach Better for Fat Loss?

When it comes to exercise and eating, things can be a bit confusing. Should I eat before cardio? Or get in a session before breakfast? If your goal is fat loss, which method is better? For years, fitness gurus have been praising the latter as the superior method for burning fat - fast. But with rising interest in exercise research and access to the Internet, skeptics finally got the answer. The thought process is that when performing cardio on an empty stomach, your body will utilize fat as fuel, over carbs. While this is true during your cardio session, the body is self-regulating, “When you burn one substrate at a given time (i.e. fat), it will tend to burn another at a later point (i.e. carbohydrate)," says Brad Schoenfeld, Ph.D., C.S.C.S, international fitness expert and the owner/operator of the exclusive Personal Training Center for Women in Scarsdale, New York. That means that even if you burn fat during your workout, the rest of the day your body is left using carbs as fuel, not fat. “Bottom line is that the complexities of the body annul any tangible benefit to performing fasted cardio, at least from a fat loss standpoint.” On top of that, eating before workouts actually increases the body’s thermogenic (fat-burning) effects after you exercise.

“There is some evidence that fat oxidation is higher when you perform cardio on an empty stomach, as the body can tap into fat as opposed to glucose/glycogen [carbohydrate],” says Brad. “However, these benefits are specific to untrained individuals exercising at low intensities -- once a person becomes experienced and/or exercises at moderate to higher intensities, the effects disappear.” Basically, once your body becomes accustomed to exercise, the higher rate of fat loss will lessen. And if you’re well past the newbie stage, the effects will be slim to none to begin with.

So while it may not make a difference in fat burn while you’re doing cardio, if you simply eat something before you get started, your body will burn more fat the rest of the day, than if you don’t. In addition, Brad said, “Most people do not perform as well [on an empty stomach], and thus cannot generate optimal intensity.” Therefore, fueling up before a sweat session will give you the energy needed to get a better workout. “From a performance standpoint, both carbs and protein work well in this regard,” says Brad, who suggests having a simple bowl of oatmeal and eggs 1-2 hours before your workout. And if you’ve only got 30 minutes, a fruit smoothie is a good option.

Since there’s not much difference in the fat burning effects of cardio before or after eating, your best bet is to find what works for you. If you feel like you can put in your all on an empty stomach, then by all means, go for it. But if you’re feeling light-headed and sluggish, you’ll be glad you ate something before you got moving.