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There's an unfortunate misconception out there that says the only way to lose body fat is by exercising at 60 to 70 percent of your maximum heart rate. At higher intensities, the theory says, your body burns more glycogen, or stored carbohydrates, instead of fat.
Never has there been a truth so partial.
While your body does use more fat for energy at lower intensities, you need to go a step further and look at the bottom line: Calories burned.
More specifically, if you burn more calories-any kind of calories-than you consume, you'll lose body fat.
"We've taken a simple thing and made it so complicated, it's ended up creating a roadblock for a lot of people," said Richard Wolff, RD and director of the Center for Nutrition at Elgin Nautilus. "First of all, there's never been a study to demonstrate that the amount of fat you burn during exercise is related to the amount of fat you actually lose. There's absolutely no scientific evidence to show a relationship between those two."
"A calorie is a calorie," agreed April Hernan, a certified personal trainer and owner of Fitness Network, Inc. in Batavia. "Even if you're doing something for 10 minutes, you're still expending energy, and if you're trying to expend more than you take in, that's going to count."
But even more important, if you're a cardiovascularly fit individual who happens to have some excess body fat, there's no reason you shouldn't exercise at higher intensities or try some interval training if you want to lower your body fat percentage.
A study at the University of Texas reported in the Jan. '95 issue of Bicycling magazine illustrates why.
The study showed that a moderately fit person cycling at 65 percent of their max heart rate burns about 220 calories in 30 minutes. And 50 percent of the calories burned are fat calories.
When the intensity is 85 percent of max, the calorie burn jumps to 330. Although only about a third of the calories burned are fat calories, the total fat calories (110) is the same (1/3 of 330 vs. ½ of 220). And at the higher intensity, the cyclist burns 100 extra calories in the same amount of time.
"And it doesn't matter if those calories are from fat, protein, or carbohydrates, it's gone; the body has to replace it, and it uses fat stores to do it," Wolff pointed out.
Does that mean you should always exercise as hard as you can?
Absolutely NOT.
If you're not in good cardiovascular shape yet, exercising at 80 or 85 percent of your max heart rate is not only very difficult to sustain for more than a few minutes, but it's very stressful on your heart. You'll also be increasing your risk for injury and burn out.
Get in the exercise habit and improve your cardiovascular fitness, Hernan advised, "once you've achieved the health and fitness level to sustain a higher exertion level, then go for it!"
© Copyright 1994 Paula Lauer