Weight Loss Q&A

Q. I'm 4-foot-11 and just entered two different weights into an online BMI calculator. My current weight (120 pounds) gave a BMI of 24.2. My weight six months ago (130 pounds), when I was lifting weights and running, gave a BMI of 26.3. Now that I've slacked on my training, my clothes feel tighter, so why is my BMI lower than it was before? Is the calculator accurate? Isn't BMI supposed to estimate your body-fat percentage?

A. Yes, your calculator is accurate, but Body Mass Index (BMI) is "only a rough indicator of body fatness," says Tim Lohman, Ph.D., an exercise physiologist in the physiology department at the University of Arizona in Tucson. "The estimate can be off 5 percent or more." BMI reflects total weight in relation to height without distinguishing, as body-fat tests do, between fat weight and lean body mass (the weight of your muscle, bones, organs and tissue). For lean, muscular people, BMI can greatly overestimate body fatness, Lohman says.

BMI is commonly used as a health measure because no complicated testing is involved. You simply plug your height and weight into a BMI calculator. For the general population, there is a correlation between height, weight and body fat. For an athlete or someone who is very muscular, however, the correlation may not necessarily apply. That's because, in general, someone who weighs more is fatter; but with muscular people a higher weight doesn't necessarily mean fatter, it may mean more muscle. In your case, a heavier weight clearly did not reflect an increased body-fat percentage. To track changes in your body fat, ditch BMI and undergo one of the more reliable body-fat tests, such as skin-fold calipers, bioelectrical impedance, DXA or the Bod Pod.

Q. I was on a high-protein diet and lost 20 pounds. But now I can't stand the sight of beef, chicken and tuna. I've cut way back on protein, but I've gone up two whole dress sizes. I am so upset. Why did this happen?

A. "In all likelihood, you've been gaining weight because you've been eating more calories," says Seattle nutritionist Susan Kleiner, Ph.D., R.D., author of Power Eating, Second Edition (Human Kinetics, 2001). High-protein diets tend to succeed, at least in the short term, not because protein has some magical power but because these diets are low in calories -- some as low as 1,200 per day. Once you stopped following the diet, you may have increased your calorie intake inadvertently. Just by eating an extra 100 calories per day - half a 3-ounce bagel - you can gain nearly 1 pound a month.

Some of your weight gain may also be due to replacing protein with refined carbohydrates, such as crackers, white bread and other processed foods. Refined carbs, which contain negligible amounts of fiber, have less staying power (i.e., you'll be hungry again sooner) than protein-rich foods or even complex carbs such as whole grains, vegetables and fruits.

Start eating more protein, just not as much as before and from a wider variety of sources. "Try beans, tofu, peanut butter and eggs," Kleiner says. "And get a good cookbook so you can try new preparation methods for meat, chicken and fish." Watch your portion sizes and keep a food diary for a week so you can monitor your calorie intake.

These are better strategies than returning to a high-protein diet. "The problem with these diets," Kleiner says, "is that they get really boring, don't contribute enough carbs to fuel a good exercise program and tend to be very high in saturated fat and cholesterol, which makes them very disease-promoting." Work on developing a more balanced approach to eating that you can maintain for the rest of your life.