Your BMI (body mass index) is a fairly good indicator of how much body fat you have. Health professionals use it to screen for possible weight problems in adults, but it doesn't paint a full picture of your health. Here's how to get your score, what the number tells you, and what it doesn't.

What's your BMI? It's calculated from your height and weight, using this equation: weight (in pounds), divided by height (in inches) squared, then multiplied by 703. A woman who is 165 pounds and 5 feet 3 inches tall (or 63 inches) has a BMI of 29.2. An online BMI calculator can do the math for you (try

What it means: For adults 20 and older, if your BMI is 30 or higher, you are considered obese — more than one-third of American adults fall into this category, and thus may have a higher risk of a number of serious health problems, including heart disease and type-2 diabetes. BMIs from 25 to 29.9 are categorized as "overweight"; 18.5 to 24.9 are "normal" or "healthy" weight; and a BMI of less than 18.5 is considered "underweight" — which recent research suggests puts people at as high a risk of dying as obese people.

What it doesn't mean: BMI measurements don't differentiate between fat and muscle, so trained athletes, for example, may have a high BMI because of more muscle, not body fat. The number also doesn't consider gender or age – at the same BMI, women tend to have more body fat than men, according to the Centers for Disease Control and Prevention; and older people, on average, have more body fat than younger adults. BMI is a good gauge of your risk for possible obesity-related problems, but it's not meant to diagnose health. Waist circumference, for example, is another important factor — excessive abdominal fat has been linked to an increased risk of coronary artery disease, and high blood pressure, among other conditions. Talk to your doctor to determine your risk and whether you should lose weight.

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