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Do You Burn More Fat When Exercising on an Empty Stomach?

Does exercising before breakfast burn more calories than working out after a meal? Get-Fit Guy has the surprising answer based on the latest scientific research.

By
Ben Greenfield
2-minute read

In the episode A Day in the Life of Get-Fit Guy, you learned that I’m a fan of doing some easy fasted cardio in the morning, such as yoga or a light walk.

So I was naturally interested in a recent study that looked into whether there is any difference in how much fat you burn during the day (scientifically referred to as “24-hour fat oxidation”) when you exercise in a fasted state rather than exercising in a fed state.

The scientists measured the caloric burn of 9 young male endurance athletes after they performed a session of 100 minutes of exercise before breakfast (aka, fasted) and 100 minutes of exercise after lunch (aka, fed). The amount of calories they ate were “equal” to the amount of energy burned during the exercise sessions, meaning they weren’t being fed a low calorie diet per se.

So what did the researchers find?

Turns out, the more you are carbohydrate “depleted” during exercise (such as you would be when exercising in a fasted state), the higher your 24-hour fat burn. Not only that, but when you do your exercise in a fasted state before breakfast, you burn the highest amount of fat throughout the day - even compared with someone who does the same amount of exercise, eats the same amount of calories, but works out after lunch or before dinner (in a fed state).

Finally, I should caution you that this entire study was done with aerobic exercise, which is far less stressful and energy depleting than high intensity intervals or weight training. For those harder sessions, I would recommend eating a little bit beforehand, as it will help you to maintain a higher exercise intensity and get more bang for your buck out of the workout session.

But for an easy cardio day, you’ll benefit most by doing that easy cardio in the morning before breakfast.

Do you have more questions about morning fasted exercise and fat burning? Head over to Facebook.com/GetFitGuy and join the conversation!

About the Author

Ben Greenfield

Ben Greenfield received bachelor’s and master’s degrees from University of Idaho in sports science and exercise physiology; personal training and strength and conditioning certifications from the National Strength and Conditioning Association (NSCA); a sports nutrition certification from the International Society of Sports Nutrition (ISSN), an advanced bicycle fitting certification from Serotta. He has over 11 years’ experience in coaching professional, collegiate, and recreational athletes from all sports, and as helped hundreds of clients achieve weight loss and fitness success.