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Q. Why do you use the BMI, and is it useful for weight lifters?

The Body Mass Index (BMI) is a simple way for men and women to estimate body fat based on their height and weight. From the BMI, it is possible to determine your healthy weight range.

One of the limitations of BMI is that it can over-predict overweight or obesity in people who are lean and muscular. For instance, someone who is 5'10" and 220 pounds, with 12% body fat, would be considered obese based on BMI standards. Obviously, someone with 12% body fat is not obese.

Is your question here?

• Why do you use the BMI, and is it useful for weight lifters?
• Does aerobic exercise interfere with muscle gains from weightlifting?
• Should I hold off on weight training until I lose weight?
• How much exercise should I do?
• I don't have time to exercise. I hate exercise. 60 minutes a day?
• Where do I start if I have never exercised?
• What should my heart rate be during exercise?
• My weight has plateaued. What do I do?
• What's the bottom line to weight loss?
• What if I am physically unable to exercise due to a medical condition?
• What is interval training?
• What's the difference between the fat burning mode vs. cardio mode on the machines at the gym?
• What is basal metabolic rate?
• Is personal assistance available to me as I use the WebMD Weight Loss Clinic plan?

The scientists who developed the BMI guidelines readily admit to this limitation. But their rationale is that most Americans are not lean and muscular and so for most people, the BMI is an accurate assessment of body fat, percent overweight, and increased health risk.

It is important to know that people who are classified as overweight or obese can be still be healthy as long as they are fit. In one well-known study, fit people with BMIs that classified them as overweight or obese were healthier and lived longer than unfit people who were at normal weight.

The BMI, for the majority of Americans, is the most up-to-date and scientifically sound method available for determining healthy weight. To find our your current BMI, go to Weight Loss Goals on the WebMD Weight Loss Clinic home page.

Q. Does aerobic exercise interfere with muscle gains from weightlifting?

If you're training for an endurance event like a marathon, when you might run 60 miles or more per week, you'll almost always see a decrease in your muscle mass. For most of us, who do more moderate amounts of physical activity, there will be minimal, if any, loss in muscle mass -- so there's nothing to worry about.

If you do plan on lots of aerobic exercise and are concerned about losing muscle, try starting with 20-30 minutes of moderate aerobic exercise (at 50% to 70% of your maximum heart rate) two to three days per week, and see how it goes.

Q. Should I hold off on weight training until I lose weight?

Absolutely not. Lifting weights will not only help you lose weight, but maintain the loss. Here's why:

• Muscle keeps your metabolism revved up, burning calories, fat, and glucose (sugar).
• When you lose weight, up to 25% of the loss may come from muscle, resulting in a slower metabolism. Weight lifting will help preserve or rebuild any muscle you lose by dieting.
• Muscle helps you with aerobic exercise. The stronger you are, the better you will be at any aerobic activity.
• Weight training improves your body's muscle-to-fat ratio (you end up with less body fat and more muscle), which improves both your health and your fitness level.
• Gaining muscle will help you look better as you define and tone your physique.
• Building strength helps you feel good about yourself. Although the scale may show a slight weight gain when you start lifting weights (usually five pounds or less), you probably won't look heavier because the gain is in muscle, and your clothes may even fit more loosely. And since muscle is so important for health, fitness, and maintaining your weight, you want as much as possible.

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