“Fat-burning” workouts: founded in fact or fiction?

At some point you’ve probably heard the term “fat-burning,” and if you’ve ever set foot on a piece of cardio equipment it probably had a “fat-burning” mode. The implication is that there is something especially important about burning fat in maximizing weight loss.

Weight loss however, is a function of creating a calorie deficit (taking in fewer calories than you burn), and not the substrate (carbohydrate, protein, or fat) that your body is fueling on. In fact your body is always burning both carbohydrate and fat. As the intensity of the activity that you are engaged in increases the percentage of fat you are burning decreases, while conversely, the percentage of carbohydrate (and total calories) you burn increases.

Author Barry Sears, PhD, was half right when he put the following bullet point on the back cover of his, one time best selling, diet book The Zone:

“You can burn more fat watching TV than by exercising.”

It is true that the percentage of fat you are fueling on is highest when you are doing the least! That being the case, if you really want to go for fat-burning, why not just stay on the couch!

The facts: when total exercise calories are equal, there is no significant difference in weight (or fat) loss between low-intensity and high-intensity workouts. But the time it takes to burn the calories is substancially more at low-intensity!

Several years ago I attended a workshop by Cedrick Bryant, PhD, chief exercise physiologist with Stairmaster. After discussing some research and the study referenced below, one of the questions he was asked was, “why do equipment manufacturers continue putting fat-burning modes on their equipment when they know it’s misleading?” Bryant’s direct (and without hesitation) answer was refreshing:

“As long as the marketing department trumps the exercise physiology department, there will be fat-burning-modes on cardio equipment.”

So what is the best exercise for weight loss? The best exercises for weight loss are the ones you will do! If you want to get the most bang for your buck however (burn the most calories per minute), then gradually increase the intensity that you work out at.

You should also be aware that the current recommendations for weight loss (and maintenance) are that you shoot for a minimum of 2,000 calories of physical activity per week. As you can see is the chart below (based on 150-pound person), it only takes 4 hours a week of high-intensity exercise to burn 2,000 calories, while it would take over 13 hours of low-intensity activity to hit that mark!

So, reaching the 2,000 calorie target requires choosing (and maybe compromising) between the amount of time you want to spend exercising, the type of activities you like to engage in, and the intensity level you like exercising at.

Just remember; go for the calories, not the fat!

If this is the kind of information you appreciate, you may also like my book: The NEW Healthy Eating & Weight Management Guide.

Best,
-Dorene

Is there a question about weight loss or dieting that you want answered? Comment here, or email me at dorene@beyonddiets.com.

References:
Zelasko, CJ. Exercise for Weight Loss: What are the facts? J Am Diet Assoc. Dec 1995;95:1414-1417.