Overweight and obesity are defined as abnormal or excessive fat accumulation that impair health.
The simplest way to assess body fatness in clinical practice is with the body mass index (BMI). BMI is calculated as measured body weight (kg) divided by measured height squared (m²). The World Health Organization (WHO) defines “overweight” as a BMI equal to or more than 25, and “obesity” as a BMI equal to or more than 30. Many people in the overweight range of BMI 25–29.9 kg/m² will become obese in their lifetime. The BMI numbers apply to both men and women. However, it should be considered as a rough guide because it may not correspond to the same degree of fatness in different individuals. Also, some very muscular people may have a high BMI without health risks.