Posted on: Wednesday, September 8, 2004

SHAPE UP
Crunching calories

Greg Taylor • The Honolulu Advertiser

By Charles Stuart Platkin

First it was calories, then fat, and now carbs — what next? Would you believe calories are back in vogue? Even the U.S. Food and Drug Administration is considering revising the Nutrition Facts panel to make the word "calories" appear even larger.

How do you know how many calories you should be eating, and will knowing help you lose weight?

Calories at rest

To figure out your total daily calorie needs, you must determine your basal metabolic rate (BMR, sometimes referred to as resting metabolic rate). That's the number of calories needed to support the unconscious work of your body (e.g., heartbeat, breathing). Yet, two people with the same height, weight, gender and age can have entirely different BMRs. "In fact, one of the biggest determinants of BMR is body composition — specifically, the ratio of muscle to fat," says Linda Bandini, a professor of nutrition at Boston University. The more muscle you have, the more calories you burn at rest.

Are they accurate?

There are several formulas for figuring your BMR. "However, many of these equations have an accuracy of plus or minus 10 percent," says Cynthia M. Goody, a professor of nutrition at the University of Cincinnati.

That can mean the difference between losing or gaining 20 pounds.

Using a scientific instrument such as an indirect calorimeter gives a relatively accurate BMR.

"But these can be time-consuming and expensive," says Dr. William H. Dietz, director of the Division of Nutrition and Physical Activity at the Centers for Disease Control and Prevention in Atlanta.

There are inexpensive, new hand-held devices such as the BodyGem that do give an accurate BMR. Health clubs such as 24 Hour Fitness will test you for a small fee.

Then you're all set, right?

Not so fast.

You probably think once you've determined your BMR, all you have to do to lose weight is cut down on the number of calories you consume. But that's not the whole story.

"Knowing your metabolic rate basically tells you how many calories you need to operate your body if you do nothing — that's all," says Gary Granata, director of the Applied Physiology Laboratory at the Ochsner Clinic Foundation in New Orleans.

"If you simply cut calories from your BMR, you will lose weight, but the wrong kind of weight — mostly lean muscle tissue."

What about activity?

After you figure out your resting metabolism, you need to factor in your activity level. That's broken down into categories from "sedentary" (you sit most of the day and don't exercise at all), which would mean you tack on about 20 percent more calories, all the way to "extreme activity" (heavy manual labor or competitive athletics), which would let you more than double the calories needed to maintain your weight.

"Trying to estimate someone's activity level is no easy task, and standards can easily be misapplied. What is moderate activity for an elite athlete is quite different from what's moderate for the average Joe," says Granata.

For instance, a competitive athlete might burn 2,400 calories per day at rest. Double that, according to the guidelines for physical activity, and that person's caloric needs should be 4,800. But someone training for the Tour de France might actually burn 10,000 calories per day — so the numbers can be significantly inaccurate.

Will you lose weight?

"Figuring out your caloric needs should be used as a guideline — sort of a starting point — but make sure to combine that with weighing yourself at least every 30 days. The scale doesn't lie. Then adjust your eating accordingly," says Dr. George L. Blackburn, director of the Center for the Study of Nutrition Medicine at Harvard Medical School in Boston.

Dietz has an even less favorable view. He takes a "why bother?" of the BMR approach. "It creates an illusion you're correctly calculating your caloric balance, and it can be off by as many as 400 calories per day — that's significant."

So just weigh yourself on a regular basis and adjust your diet accordingly, say the experts.

Simple is better

Don't waste time with fancy gadgets. There are many Web sites (e.g., kidsnutrition.org/caloriesneed.htm) that let you plug in your information and give you a relatively accurate BMR.

Or you can use a simple formula such as figuring 11 to 12 calories per pound of body weight for your BMR and factoring in the proper percentage for your physical activity level.

For the sedentary level, multiply your BMR by 1.2. Or:

• Light activity: 1.3 to 1.4.
• Moderate activity: 1.5.
• Very active: 1.6 to 1.7.
• Extreme activity: 2 to 2.4.