Calorie counters and why you can't trust them...

Researchers at Appalachian State University have revealed why the calorie counters on exercise machines could leave you thinking that you've burned more calories than you really have.

The study tracked a group of overweight women taking part in an aerobic exercise program. The program involved 45 minutes of aerobic exercise, performed at 70-80% of maximum heart rate.

Calorie counters

The average number of calories burned during each workout was estimated to be roughly 255 calories. However, the research team points out that this figure doesn't take into account the difference between net and gross caloric expenditure.

• Gross energy expenditure refers to the number of calories you burn during exercise plus your metabolic rate.

• Net energy expenditure refers to just the number of calories you burn during exercise.

Because calorie counters on some (but not all) exercise machines display gross energy expenditure, the figures they give can be misleading.

For example, in the present study, the gross number of calories burned was 255. In contrast, the net figure (remember, the net figure represents the "real" number of extra calories you've burned) was just 187 calories. In other words, if you rely on the numbers given by the calorie counters, it might appear that you've burned 36% more calories than you really have.

So, why does this matter? Each pound of fat contains the equivalent of approximately 3,555 calories. Using the data given in this study, you would need 19 aerobic workouts, each lasting 45 minutes, to lose just one pound of fat.

Keep this in mind the next time you train with the goal of burning a specific number of calories. For example, if you go to the gym to burn 300 calories, simply add 30%, and aim for 390 calories instead.

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Reference
Utter, A.C., Nieman, D.C., Shannonhouse, E.M., Butterworth, D.E., & Nieman, C.N. (1998). Influence of diet and/or exercise on body composition and cardiorespiratory fitness in obese women. International Journal of Sport Nutrition, 8, 213-222