Does exercising before eating breakfast help you burn more body fat?


Nope. You burn more calories from fat in the morning but that's different than burning more body fat.


Laurent Amzallag- Personal Trainer of 25 years serving the DMV- Balance Gym and Equinox Sports Club Washington, D.C.

Isabel Maples- registered Dietitian Nutritionist and spokesperson for the Academy of Nutrition and Dietetics

Todd Miller-Director of Weight Management and Human Performance Lab at George Washington University and Director of Graduate Studies, Department of Exercise and Nutrition Sciences

The Journal of Physiology: "Training in the fasted state improves glucose tolerance during fat-rich diet."


To kick off the new year we're trying to help you get fitter, faster and nip fat, well, in the butt.

This question came from Kandy Hutman, who said she read online that you could burn more body fat by working out before eating breakfast.The idea is that the body is still waking up from its 'fasted state,' and uses food stored from the day before rather than new food it's digesting.

Our researchers found the genesis of this idea in a 2010 study.

In a nutshell, 28 men were split into three groups. One group did not exercise, they were the "control group." The second group exercised after eating a carb-heavy breakfast and continued consuming carb-drinks into their workout. The third exercised before eating.

All participants ate of 50 percent fat, 40 percent carbs and 10 percent protein ranging from 3,000-4,500 calories daily . At the end of six weeks, the control group gained lots of weight, the post-breakfast exercisers gained less weight and the group that exercised before breakfast actually lost weight.

"While the journal article shows that the group that ate the carbs during the workout gained more weight than the fasted group, they did not gain more fat," Todd Miller, head of George Washington University's fat and metabolism lab explained. "The increased wight could have been due to an increase in muscle mass in the fed group."

George Washington University Proffesor Todd Miller hooked up to a Metabolic Cart which measures your oxygen consumption, the gold standard for calculating metabolism. Miller is in the Weight and Human Performace Lab, which he heads in Ashburn.

After the study was published in November 2010, numerous articles followed, explaining the benefits of exercising before breakfast. Many claimed an a.m. sweat sesh helped burn more body fat.

Our Verify experts say, that's just not right.

When you exercise, your body turns to carbs for energy first. But if you haven eaten, your carb storage is low, and so your body will use it up and then go after stored fat.

Let's say you burn 500 calories before breakfast, a greater percent of those calories being burned are coming from fat--70 percent fat, 30 percent carb. Let's say you eat breakfast, and now you get on the treadmill.You burn that same 500 calories but now you're running on 70 percent carb and 30 percent fat.

Whether it's fat or carbs doesn't determine the size of your gut.

"The fuel that's burned during the exercise itself has nothing to do with how much fat loss you lose over time," Miller said. "What determines how much fat you lose over time is the difference between how many calories you eat and how many you burn throughout the day."

"When you exercise on an empty stomach the body will use more fat as a source of energy because now your body has depleted itself of the glycogen storage (metabolized carbs in the liver and muscle)," DC Personal Trainer Laurent Amzallag said.

Carbs are the preferred energy "pantry" because they metabolize quickly and turn into sugar, Amzallag explained. Fats on the other-hand are a sort of back-up energy pack that requires a lot of oxygen to break down and therefore burns most effectively when you're sleeping or resting in the 23 hours after an intense workout.

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How much time do you have before your body depletes it's carbs?

"You have 90 minutes of glycogen, after that it will tap out,"Amzallag explained. Your liver and muscles can store about 1,800 to 2,000 calories of the stuff.

So the body does burn more calories from fat, but that doesn't translate into more body fat burned.

Isabel Maples, a registered dietitian and nutritionist who has counseled athletes and preteens and now seniors and hospice patients, recommends eating an egg or toast before an early morning workout.

"Breakfast offers fuel, fluids, but also focus," Maples said. "If you're lightheaded, dizzy, then you're not going to be able to workout at your best."


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