Nearly two-thirds of the United States population is overweight. There are many ways to determine if a person is overweight, but experts believe that a person's body mass index (BMI) is the best way to assess an adult's weight in relation to their height.
A BMI from 18.5 to 24.9 kg/m2 is considered normal.
Adults with a BMI of 25 to 29.9 kg/m2 are considered overweight. There are exceptions. For example, an athlete may have a higher BMI but not be overweight.
Adults with a BMI of 30 to 39.9 kg/m2 are considered obese.
Adults with a BMI greater than or equal to 40 kg/m2 are considered extremely obese.
Anyone more than 100 pounds overweight is considered morbidly obese.
A person with a high BMI may have a normal amount of body fat if they have a lot of muscle tissue. However, the risk of death and disease is increased for adults who are overweight and obese.
Klein S, Fabbrini E, Romijn JA. Obesity. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 36.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.