BMI, or body mass index, is a fairly accurate estimate of body fat in most individuals and commonly used to help determine risk for certain chronic diseases. BMI is determined using an individual’s current height and weight. People with BMIs that are very low or very high have an increased disease risk. Population groups where BMI may not be reliable include athletes with lots of lean muscle mass, or the elderly, who may have decreased muscle mass or bone density.
Determining BMI
According to the American Dietetic Association, BMI can be determined using the following formula: (weight (in pounds) X 703) / height (in inches) / height (in inches). The American Dietetic Association’s website also provides a BMI calculator to help quickly and easily calculate BMI. BMIs below 18.5 are considered underweight, 18.5 to 24.9 normal weight, 25.0 to 29.9 overweight and 30.0 and above obese. Being in the overweight or obese BMI category increases an individual’s chronic disease risk.
High BMI Prevalence
Obesity, with BMIs 30 and above, has reached epidemic proportions worldwide. According to the World Health Organization, or WHO, over 1 billion adults globally are overweight, with BMIs 25 to 29.9, and at least 300 million are obese. The WHO attributes the increased prevalence of high BMIs to increased consumption of sugar and saturated fat, and decreased physical activity. BMIs of 25 and above can increase the risk for developing diseases such as diabetes, heart disease, high blood pressure and some forms of cancer.
BMI and Race
The prevalence of having a high BMI of 30 or above has been shown to be associated with an individual’s race. According to the Centers for Disease Control and Prevention, from 2006 to 2008 African Americans had a 51 percent higher rate of obesity than whites, and Hispanic Americans had a 21 percent higher prevalence of obesity compared to whites.
BMI and Gender
There are gender disparities in prevalence of BMIs in the overweight and obese categories. According to the National Institute of Diabetes and Digestive and Kidney Diseases Weight-control Information Network, 64.1 percent of U.S. women are overweight or obese, with BMIs 25 and above, compared to 72.3 percent of men in the same BMI categories. The Weight-control Information Network also states that only 31.6 percent of all U.S. adults are in a healthy weight category, with BMIs of 18.5 to 24.9.
BMI and Region
Rates of high BMIs vary by region worldwide. According to the World Health Organization, obesity prevalence in China, Japan and some African nations is below 5 percent and over 75 percent in some areas of Samoa. Obesity rates in the United States vary by state. According to the Centers for Disease Control and Prevention, in 2008 there were 32 U.S. states with an obesity prevalence of more than 25 percent; Six states had an obesity prevalence of more than 30 percent.
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