Overweight refers to an excess of body weight compared to set standards. The excess weight may come from muscle, bone, fat, and/or body water. Obesity refers specifically to having an abnormally high proportion of body fat. A person can be overweight without being obese, as in the example of a bodybuilder or other athlete who has a lot of muscle. However, many people who are overweight are also obese.
How are overweight and obesity measured?
A number of methods are used to determine if someone is overweight or obese. Some are based on the relation between height and weight; others are based on measurements of body fat. The most commonly used method today is body mass index (BMI).
BMI can be used to screen for both overweight and obesity in adults. It is the measurement of choice for many obesity researchers and other health professionals, as well as the definition used in most published information on overweight and obesity. BMI is a calculation based on height and weight, and it is not gender-specific. BMI does not directly measure percent of body fat, but it is a more accurate indicator of overweight and obesity than relying on weight alone.
BMI is found by dividing a person’s weight in kilograms by height in meters squared. The mathematical formula is:
weight (kg) / height squared (m^(2)).
To determine BMI using pounds and inches, multiply your weight in pounds by 704.5,* then divide the result by your height in inches, and divide that result by your height in inches a second time. (Or you can use the BMI calculator at http://www.health.am/calculator/index.php or check the chart shown below that has calculated BMI for you.)
*The multiplier 704.5 is used by the National Institutes of Health. Other organizations may use a slightly different multiplier; for example, the American Dietetic Association suggests multiplying by 700. The variation in outcome (a few tenths) is insignificant.
Revision date: June 14, 2011
Last revised: by Janet A. Staessen, MD, PhD