July 25, 2008
Counter Fitness
Q: Can I trust the calorie counters on exercise equipment?
A: Only to a point. Calorie readouts on gym and home cardio exercise machines typically overestimate the number of calories actually burned by 10 to 30 percent, sometimes more. In a study conducted at Appalachian State University in North Carolina, subjects who exercised on five different machines burned an average of 255 calories according to the equipment displays - but only 187 calories according to the sophisticated lab equipment that was monitoring them. That's a difference of about 30 percent. Several other studies have shown similar discrepancies between machine readouts and actual calories burned. Treadmills tend to be the most accurate because they've been studied the longest and the formulas they use to determine calorie burn are the most well-established.
When a machine doesn't ask you to enter your body weight, this usually means the machine has defaulted to information based on a 150-pound exerciser. So, if you weigh less, the machine overestimates your burn rate; if you weigh more, the readout will be an underestimate.
Even top-notch machine readouts will be less accurate if you use poor form. For instance, if you clutch the front rail of the treadmill, you're making your workout much easier, and the calorie readout may be off by as much as 50 percent.
To increase the accuracy of the calorie information on a machine, punch in a weight that's about 20 percent lower than your actual weight. But even then, don't put too much stock in the number. No exercise machine will give you an exact calorie count unless you go into an exercise lab where scientists can measure your heart rate and the amount of oxygen in your lungs.
Q: My gym offers body fat testing with skinfold calipers. Should I get tested?
A: If you're aiming to slim down, getting tested every four to six months is a great way to monitor your progress. Don't get tested more frequently because, unlike scales, body-fat tests aren't sensitive to small changes. A body-fat test is more useful than the scale because it distinguishes fat loss from muscle or water loss.
What's a good score? Experts disagree on the precise numbers, but the general consensus is that men should not exceed 20 percent to 22 percent body fat. For women, the high end of healthy is somewhere between 26 percent and 30 percent.
Still, because your disease risk is influenced by the location of your fat and other factors, it's impossible to equate a body-fat score with increased risk of disease. A woman who is 30 percent fat but carries the bulk of her fat in her hips and thighs is likely to be at lower risk for diabetes and heart disease than a woman with the same body-fat percentage who carries more fat in her abdominal area.
Just keep in mind that no body-fat testing method is entirely accurate, so don't take your results too literally. Skinfold calipers can be accurate within four percentage points, but only if the tester is skilled at separating fat from muscle and pinches precisely the right spots. Also, it's important that the tester use a formula that takes age into consideration. Fat tends to move inward with age, but calipers pinch only fat near the skin; so, if your tester uses a formula designed for 20-year-olds, the amount of fat pinched by the caliper might underestimate your total body fat.
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About Our Expert: Suzanne Schlosberg is the author of The Ultimate Workout Log and The Essential Fertility Log and coauthor of Fitness for Dummies and The Fat-Free Truth. She's a health and fitness writer living in Bend, Oregon.(login / or create an account to comment)