Tests, Tools Can Help You Manage Calories and Weight

Q:  We are often told that the key to weight management is to keep caloric intake at or below the level of caloric output (i.e., don't eat more than you burn off). Is there a test to determine how many calories we should eat in order to lose, gain, or maintain our weight?

I have heard of a non-invasive test being offered by a dietetic clinic that supposedly tells you your metabolic rate and hence the number of calories you should consume to manage your weight. But this sounds too good to be true -- is it?

A:  Probably what a dietetic clinic can do is calculate your metabolic rate based on your description of your daily activities. This calculation is only an estimate of your metabolic rate, but, in all practicality, it is the best anyone can do. You could duplicate this service yourself if you are good with numbers.

First, you can estimate your basal metabolic rate by multiplying your body weight in pounds times 10. So, if you are 150 pounds, you would need about 1500 calories a day to maintain weight. But this formula does not factor in your build or activity level.

The World Health Organization (WHO) recommends a more complicated approach, based on your age and gender. They suggest calculating a basal metabolic rate (BMR) and then multiplying this number times an "activity factor." Unfortunately, the activity factor is still only your estimate of your activity level.

While everyone knows that you can burn calories with aerobic exercise, your energy use is also significantly affected by fidgeting or small tasks. If you are buzzing about taking care of small children, for instance, that may be equivalent to several hours of walking for exercise.

For the mathematicians, here are the WHO formulas, where "W" stands for weight in pounds:

• Women aged 18-30: BMR = (0.028 W + 2.0) x 240
• Women aged 31-60: BMR = (0.016 W + 3.5) x 240
• Men aged 18-30: BMR = (0.029 W + 2.9) x 240
• Men aged 31-60: BMR = (0.022 W + 3.7) x 240

The "activity factor" is 1.3 for sedentary people, 1.5 for people with some regular exercise, and 1.7 for people who are very active.

A third formula is even more complicated since it is based on gender, specific age, and height. Thankfully, you can plug your numbers into an online Basal Metabolism Calculator. There is also the even more complicated Healthy Body Calculator.

If you want to be more accurate, you can diary your activities and add up how much time you typically spend doing a specific activity (for instance, 8 hours sleeping, 4 hours sitting, 1 hour swimming, etc.) You can then use the online calculator "calorie burner" at Prevention.com (this website also has a "daily calorie" calculator), or the Activity Calorie Counter.

Finally, you can diary your food intake and calculate the number of calories you typically consume (by reading food labels or by going to the USDA Nutrient Data Laboratory for calorie information on foods. If you reduce your usual calorie intake by 500 calories each day, you should lose a pound a week.

For more information on this topic, see the HealthLink article Body Mass Index Calculator and Waist Measurement.

Julie L. Mitchell, MD, MS, is an Assistant Professor of Medicine at the Medical College of Wisconsin. She practices internal medicine at the Froedtert & Medical College General Internal Medicine Clinic - East. Her column appears in the Milwaukee Journal-Sentinel.