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NIH MedlinePlus the Magazine, Trusted Health Information from the National Institutes of Health


Know Your Body Mass Index (BMI)

As a part of healthy aging, it pays to understand your body mass index (BMI), a measure of body fat based on height and weight that applies to both adult men and women.

The National Heart, Lung, and Blood Institute (NHLBI) has a Web site that lets you easily calculate your BMI just by entering your current height and weight. Visit to learn your BMI.

BMI Categories:

  • Underweight = <18.5
  • Normal weight = 18.5-24.9
  • Overweight = 25-29.9
  • Obesity = BMI of 30 or greater

According to the NHLBI guidelines, assessment of overweight involves using three key measures:

  • body mass index (BMI)
  • waist circumference, and
  • risk factors for diseases and conditions associated with obesity.

Waist Circumference

Determine your waist circumference by placing a measuring tape snugly around your waist. It is a good indicator of your abdominal fat, which is another predictor of your risk for developing risk factors for heart disease and other diseases. This risk increases with a waist measurement of over 40 inches in men and over 35 inches in women.

Besides being overweight or obese, there are other risk factors to consider:

  • high blood pressure (hypertension)
  • high LDL-cholesterol ("bad" cholesterol)
  • low HDL-cholesterol ("good" cholesterol)
  • high triglycerides
  • high blood glucose (sugar)
  • family history of premature heart disease
  • physical inactivity
  • cigarette smoking

For people who are considered obese (BMI greater than or equal to 30) or those who are overweight (BMI of 25 to 29.9) and have two or more risk factors, the guidelines recommend weight loss. Even a small weight loss (just 10 percent of your current weight) will help to lower your risk of developing diseases associated with obesity. Patients who are overweight, do not have a high waist measurement, and have fewer than two risk factors may need to prevent further weight gain rather than lose weight.

Winter 2007 Issue: Volume 2 Number 1 Page 16