EXERCISE IS AT BEST “COMPLIMENTARY” TO A DEDICATED “CALORIE RESTRICTIVE” DIET…PURE AND SIMPLE…NO REDUCED CALORIE CONSUMPTION, NO SUBSTANTIVE WEIGHT-LOSS…AND THE IDEA THAT THERE IS “AFTER-BURN” OF CALORIES FOLLOWING EXERCISE IS PURE FANTASY TOO…BUT REGULAR EXERCISE WILL HELP MAINTAIN MUSCLE MASS WHICH WILL HELP THE BODY BURN CALORIES, BUT NOT WITHOUT A GOOD DIET REGIMEN….
For some time, researchers have been finding that people who exercise don’t necessarily lose weight. A study in The British Journal of Sports Medicine was the latest to report apparently disappointing slimming results. In the study, 58 obese people completed 12 weeks of supervised aerobic training without changing their diets. The group lost an average of a little more than seven pounds, and many lost barely half that.
published online in September
How can that be? Exercise, it seems, should make you thin. Activity burns calories. No one doubts that.
“Walking, even at a very easy pace, you’ll probably burn three or four calories a minute,” beyond what you would use quietly sitting in a chair, said Dan Carey, Ph.D., an assistant professor of exercise physiology at the University of St. Thomas in Minnesota, who studies exercise and metabolism.
But few people, an overwhelming body of research shows, achieve significant weight loss with exercise alone, not without changing their eating habits. A new study from scientists at the University of Colorado School of Medicine in Denver offers some reasons why. For the study, the researchers recruited several groups of people. Some were lean endurance athletes; some sedentary and lean; some sedentary and obese. Each of the subjects agreed to spend, over the course of the experiment, several 24-hour periods in a special laboratory room (a walk-in calorimeter) that measures the number of calories a person burns. Using various calculations, the researchers could also tell whether the calories expended were in the form of fat or carbohydrates, the body’s two main fuel sources. Burning more fat than carbohydrates is obviously desirable for weight loss, since the fat being burned comes primarily from body fat stores, and we all, even the leanest among us, have plenty of those.
The Denver researchers were especially interested in how the athletes’ bodies would apportion and use calories. It has been well documented that regular endurance training increases the ability of the body to use fat as a fuel during exercise. They wondered, though, if the athletes — or any of the other subjects — would burn extra fat calories after exercising, a phenomenon that some exercisers (and even more diet and fitness books) call “afterburn.”
“Many people believe that you rev up” your metabolism after an exercise session “so that you burn additional body fat throughout the day,” said Edward Melanson, Ph.D., an associate professor in the division of endocrinology at the School of Medicine and the lead author of the study. If afterburn were found to exist, it would suggest that even if you replaced the calories you used during an exercise session, you should lose weight, without gaining weight — the proverbial free lunch.
Each of Melanson’s subjects spent 24 quiet hours in the calorimeter, followed later by another 24 hours that included an hourlong bout of stationary bicycling. The cycling was deliberately performed at a relatively easy intensity (about 55 percent of each person’s predetermined aerobic capacity). It is well known physiologically that, while high-intensity exercise demands mostly carbohydrate calories (since carbohydrates can quickly reach the bloodstream and, from there, laboring muscles), low-intensity exercise prompts the body to burn at least some stored fat. All of the subjects ate three meals a day.
To their surprise, the researchers found that none of the groups, including the athletes, experienced “afterburn.” They did not use additional body fat on the day when they exercised. In fact, most of the subjects burned slightly less fat over the 24-hour study period when they exercised than when they did not.
“The message of our work is really simple,” although not agreeable to hear, Melanson said. “It all comes down to energy balance,” or, as you might have guessed, calories in and calories out. People “are only burning 200 or 300 calories” in a typical 30-minute exercise session, Melanson points out. “You replace that with one bottle of Gatorade.”