(Weight / 2.2) / ((Height x 2.54 / 100) x (Height x 2.54 / 100))

Below 18.5 = Underweight
18.5 - 24.9 = Normal Weight
25 - 29.9 = Overweight
BMI of 30 or greater = Obesity

Body-mass index, or BMI, is used as one measure of obesity or state of being overweight. BMI is used as a baseline and, then subsequently, to measure the effectiveness of a weight loss and/or health regimen implemented in cooperation with an individual's physician and other health care providers.

Under government (NIH) guidelines, people with BMI's of 18.5 to 24.9 are considered to be at normal weight. Those with BMI's of 25 to 29.9 are considered overweight, and those with BMI's of 30 and above are considered obese. Those with BMI's of 18.5 or less are considered underweight.

Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. National Heart, Lung, and Blood Institute, in cooperation with the National Institute of Diabetes and Digestive and Kidney Disease. National Institutes of Health. June 17, 1998. Press release available at www.nhlbi.nih.gov/new/press/oberel4f.htm.