BMI for Adults

For adults 20 years old and older, Body Mass Index (BMI) is interpreted using standard weight status categories that are the same for all ages and for both men and women. For children and teens, on the other hand, the interpretation of BMI is both age- and sex-specific. For more information about interpretation for children and teens, visit BMI for Children and Teens.

How reliable is BMI as an indicator of body fatness?

The correlation between the BMI number and body fatness is fairly strong; however the correlation varies by sex, race, and age. These variations include the following examples: 3, 4

• At the same BMI, women tend to have more body fat than men.
• At the same BMI, older people, on average, tend to have more body fat than younger adults.
• Highly trained athletes may have a high BMI because of increased muscularity rather than increased body fatness.

It is also important to remember that BMI is only one factor related to risk for disease. For assessing someone's likelihood of developing overweight- or obesity-related diseases, the National Heart, Lung, and Blood Institute guidelines recommend looking at two other predictors:

• The individual's waist circumference (because abdominal fat is a predictor of risk for obesity-related diseases).
• Other risk factors the individual has for diseases and conditions associated with obesity (for example, high blood pressure or physical inactivity).

For more information about the assessment of health risk for developing overweight- and obesity-related diseases, see the Body Mass Index article.

The standard weight status categories associated with BMI ranges for adults are shown in the following table.

For example, here are the weight ranges, the corresponding BMI ranges, and the weight status categories for a sample height.

If an athlete or other person with a lot of muscle has a BMI over 25, is that person still considered to be overweight?

According to the BMI weight status categories, anyone with a BMI over 25 would be classified as overweight and anyone with a BMI over 30 would be classified as obese.

It is important to remember, however, that BMI is not a direct measure of body fatness and that BMI is calculated from an individual's weight which includes both muscle and fat. As a result, some individuals may have a high BMI but not have a high percentage of body fat. For example, highly trained athletes may have a high BMI because of increased muscularity rather than increased body fatness. Although some people with a BMI in the overweight range (from 25.0 to 29.9) may not have excess body fatness, most people with a BMI in the obese range (equal to or greater than 30) will have increased levels of body fatness.

It is also important to remember that weight is only one factor related to risk for disease. If you have questions or concerns about the appropriateness of your weight, you should discuss them with your healthcare provider.

What are the health consequences of overweight and obesity for adults?

The BMI ranges are based on the relationship between body weight and disease and death.5 Overweight and obese individuals are at increased risk for many diseases and health conditions, including the following: 6

• Hypertension
• Dyslipidemia (for example, high LDL cholesterol, low HDL cholesterol, or high levels of triglycerides)
• Type 2 diabetes
• Coronary heart disease
• Stroke
• Gallbladder disease
• Osteoarthritis
• Sleep apnea and respiratory problems
• Some cancers (endometrial, breast, and colon)

For more information about these and other health problems associated with overweight and obesity, visit Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults.

Is BMI interpreted the same way for children and teens as it is for adults?

Although the BMI number is calculated the same way for children and adults, the criteria used to interpret the meaning of the BMI number for children and teens are different from those used for adults. For children and teens, BMI age- and sex-specific percentiles are used for two reasons:

• The amount of body fat changes with age.
• The amount of body fat differs between girls and boys.

Because of these factors, the interpretation of BMI is both age- and sex-specific for children and teens. The CDC BMI-for-age growth charts take into account these differences and allow translation of a BMI number into a percentile for a child's sex and age.

For adults, on the other hand, BMI is interpreted through categories that are not dependent on sex or age.

References

1. Mei Z, Grummer-Strawn LM, Pietrobelli A, Goulding A, Goran MI, Dietz WH. Validity of body mass index compared with other body-composition screening indexes for the assessment of body fatness in children and adolescents. American Journal of Clinical Nutrition 2002;7597–985.

2. Garrow JS and Webster J. Quetelet's index (W/H2) as a measure of fatness. International Journal of Obesity 1985;9:147–153.

3. Prentice AM and Jebb SA. Beyond Body Mass Index. Obesity Reviews. 2001 August; 2(3): 141–7.

4. Gallagher D, et al. How useful is BMI for comparison of body fatness across age, sex and ethnic groups? American Journal of Epidemiology 1996;143:228–239.

5. World Health Organization. Physical status: The use and interpretation of anthropometry. Geneva, Switzerland: World Health Organization 1995. WHO Technical Report Series.

6. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults.