Afterburn? Now just another fitness myth! New study shows exercise has little impact on fat metabolism once your workout is over.

You’ve probably already heard it from me, if not you’ve heard some other fitness authority tell you that the “fat burning” zone is a myth…. It was just a catch phrase that people glommed onto, but the real truth is it was just a euphemistic term for low intensity cardio exercise.

Now another myth is being busted thanks to a new study published in “Exercise & Sports Medicine” this past April.

This not only caught me by surprise, it even surprised the lead researcher, an exercise physiologist from the University of Colorado. The article says that moderate duration exercise (of less than 1 hour) has little impact on burning fat after the workout is done. It also says that, “despite decades of research on exercise and fat metabolism, there is still no clear understanding of how exercise helps to regulate fat mass.” Yep, this is bad news for those of us who tout exercise as a way to rev up your metabolism and turn ourselves into fat burning machines. However, my world has not been completely turned upside down just yet. Some things still remain true. For example, exercise still improves the muscles’ ability to oxidize (“burn”) fat, at least while you’re in the act of exercising. The myth that has been busted is that you can still be burning fat long after your workout is done. Gone is the theory that our bodies can still be burning fat 24 hours after our last workout. Is there any such thing as “afterburn” now? According to an associate professor at the Ottowa School of Human Kinetics, unless you consider 15 – 35 minutes to be a long time, your metabolism pretty much goes back to where it was by the time you’ve finished your post-workout shower!

For the study published this past April, Edward Melanson who wrote the article, used 65 people of varying fitness levels, from highly conditioned to sedentary and various body types, from lean to obese. He had them cycle at various intensities until they each burned 400 calories. Then he monitored them closely for 24 hours afterwards. None of the subjects showed enhanced fat burning during or after their workouts. Needless to say, this was not the result most fitness experts expected to hear!
Bear in mind, this is not a license to hang up your running shoes. Regular exercise is still a key factor in improving and maintaining your health. Plus, you still burn many more calories exercising than watching TV and, your body still looks a heck of a lot better with muscle tone than flab.
The other rule that hasn’t changed is that the number of calories you burn during exercise is still under your control. You can work out longer, or more often, or at higher intensity to increase your caloric expenditure. Doing intervals while you jog, cycle or swim will up the numbers of calories you expend. You can also try learning a new physical activity. You always work harder when you’re less efficient at something. Whichever method you chose, you just have to hit the grand total of 3,500 burned calories. Whether it’s a fat, protein or carbohydrate calorie, torching 3,500 of those babies will lead to a pound off of you. Will it be a pound of fat? Unfortunately when we lose weight, it is usually a combination of fat and muscle (we don’t count water weight). So, be sure you’re eating enough protein.
The take home message here is the oldest equation in the book. Weight loss is a simple mathematical equation of calories in vs. calories out. If you burn more calories (of any type) than you consume, you will lose weight. The more calories you burn, the faster that will happen. This should not be a news flash to anyone.
On a final note, your body’s basal metabolic rate in general is a very powerful weight loss tool. Think of it this way, a typical 120 lb. woman burns about 1200 a day doing nothing more than breathing. (A good rule of thumb to guesstimate your BMR is to take your body weight and multiply by 10). Now, add a good hour or so of moderately hard to hard exercise a day to burn off an extra 400 – 700 calories, and you’ll be dropping the LB’s in no time!
*Please refer back to previous blogs to learn more about figuring out your basal metabolic rate and interval training.

Jill Brown
Jill Brown
Hi, I'm JillI am a Los Angeles based Fitness + Nutrition Coach. With 20+ years of experience in teaching, training and continuing my education, I have transformed thousands of lives through fitness and healthy lifestyle changes.