• Body Mass Index

• Waist circumference

• How does overweight or obesity affect my health?

• What should I do if my BMI or waist measurement is too high?

• Additional Reading

Health care providers use body mass index (BMI) and waist circumference measures to assess a person's risk of developing diabetes, heart disease, or other health problems. This fact sheet tells you how to measure your BMI and waist circumference, and what these measures mean for your health.

Today, 64.5 percent of adults in the U.S. are overweight or obese. How do you know if you are among them? Two simple measures, body mass index (BMI) and waist circumference, provide useful estimates of overweight, obesity, and body fat distribution.

BMI measures your weight in relation to your height, and is closely associated with measures of body fat. You can calculate your BMI using this formula:

For example, for someone who is 5 feet, 7 inches tall and weighs 220 pounds, the calculation would look like this:

A BMI of 18.5 to 24.9 is considered healthy. A person with a BMI of 25 to 29.9 is considered overweight, and a person with a BMI of 30 or more is considered obese.

You can also find your weight group on the chart below. The chart applies to all adults. The higher weights in the healthy range apply to people with more muscle and bone, such as men. Even within the healthy range, weight gain could increase your risk for health problems.

To use this table, find the appropriate height in the left-hand column labeled Height. Move across to a given weight. The number at the top of the column is the BMI at that height and weight. Pounds have been rounded off.

Source: Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, September 1998.

* Without Shoes
**Without Clothes

Because BMI does not show the difference between fat and muscle, it does not always accurately predict when weight could lead to health problems. For example, someone with a lot of muscle (such as a body builder) may have a BMI in the unhealthy range, but still be healthy and have little risk of developing diabetes or having a heart attack.

BMI also may not accurately reflect body fatness in people who are very short (under 5 feet) and in older people, who tend to lose muscle mass as they age. And it may not be the best predictor of weight-related health problems among some racial and ethnic groups such as African American and Hispanic/Latino American women. But for most people, BMI is a reliable way to tell if your weight is putting your health at risk.

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How does overweight or obesity affect my health?

Extra weight can put you at a higher risk for many health problems including type 2 diabetes, high blood pressure, and heart disease.

Extra weight can put you at higher risk for these health problems:

• type 2 diabetes (high blood sugar)

• high blood pressure

• heart disease and stroke

• some types of cancer

• sleep apnea (when breathing stops for short periods during sleep)

• osteoarthritis (wearing away of the joints)

• gallbladder disease

• liver disease

• irregular menstrual periods

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What should I do if my BMI or waist measurement is too high?

• your BMI is 30 or above, or

• your BMI is between 25 and 30 and you have:

  • two or more of the health problems listed above or

  • a family history of heart disease or diabetes, or

• your waist measures over 35 inches (women) or 40 inches (men)-even if your BMI is less than 25-and you have:

  • two or more of the health problems listed above or

  • a family history of heart disease or diabetes.

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Additional Reading

Healthy Eating and Physical Activity Across Your Lifespan: Better Health and You. NIH Publication No. 02-4992. June 2002. Available from WIN.

Understanding Adult Obesity. NIH Publication No. 01-3680. October 2001. Available from WIN.

Active at Any Size. NIH Publication No. 04-4352. Reprinted April 2004. Available from WIN.

Weight-loss and Nutrition Myths.NIH Publication No. 04-4561. Reprinted March 2004. Available from WIN.

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The Weight-control Information Network (WIN) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health, which is the Federal Government's lead agency responsible for biomedical research on nutrition and obesity. Authorized by Congress (Public Law 103-43), WIN provides the general public, health professionals, the media, and Congress with up-to-date, science-based health information on weight control, obesity, physical activity, and related nutritional issues.

WIN answers inquiries, develops and distributes publications, and works closely with professional and patient organizations and Government agencies to coordinate resources about weight control and related issues.

Publications produced by WIN are reviewed by both NIDDK scientists and outside experts. This fact sheet was also reviewed by Robert Kushner, M.D., Professor of Medicine, Northwestern University and Medical Director, Wellness Institute, Northwestern Memorial Hospital, and Domenica Rubino, M.D., George Washington University Weight Management Program.

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NIH Publication No. 04-5283
Reprinted June 2004