CDC & BMI for Obesity

The Centers for Disease Control and Prevention is one of the premier agencies in the United States organized to track health problems, promote research and institute prevention strategies. As obesity grows at epidemic levels, the CDC uses many of its resources to monitor and stem the tide against growing rates of overweight and obesity. The CDC promotes the use of the body mass index, or BMI, to screen people who are at risk of becoming obese and having related health problems.

BMI

BMI is a measure calculating your weight in relation to your height. The formula involves dividing your weight in kilograms by the square of your height in meters. The resulting number tells health care providers about your level of body fat and whether you are obese or at risk for conditions such as heart disease and metabolic syndrome. A BMI of 30 or greater classifies you as obese. Children's BMIs are measured in percentiles; the 95th percentile or greater is considered obese.

CDC Uses BMI to Track Obesity

The CDC supports major survey tools to monitor the rates of obesity in the United States. One is the Behavioral Risk Factor Surveillance System. The BRFSS is reportedly the world's largest ongoing health survey, conducted by phone each month, tracking health conditions, including obesity. In 2009, the CDC used the BRFSS to get national, state and county-level data on the prevalence of obesity. Obesity was calculated by asking respondents their weight and height and calculating their BMI. The CDC also supports the National Health and Nutrition Examination Survey, or NHANES, which assesses the health and nutritional status of adults and children in the United States. NHANES also provides national estimates of obesity by interview and physically examining samples.

Obesity Trends in the United States

More than two-thirds of adults in the United States are overweight or obese, and one in three children is overweight and obese, according to the Journal of the American Medical Association. The CDC has tracked the states and counties with the highest proportions of people with BMIs greater than 30. In 2007, more than 30 percent of the populations of West Virginia, the Appalachian counties of Tennessee and Kentucky, much of the Mississippi Delta, and a southern belt extending across Louisiana, Mississippi, Alabama, Georgia, and the coastal regions of the Carolinas was obese.

BMI Not a Perfect Screening Tool

The CDC acknowledges that BMI is not always the best and most reliable indicator of obesity. It states, for example, 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." The BMI formula is simply a starting point for your health care provider to determine whether you need further testing.