Testtömegindex

Testtömegindex, commonly referred to in English as body mass index (BMI), is a simple measure used to classify people according to body mass. It is defined as BMI = weight in kilograms divided by the square of height in meters (kg/m^2).

For adults, standard categories widely used by health organizations are: underweight (<18.5 kg/m^2), normal weight (18.5–24.9), overweight (25–29.9), and obesity (≥30). Some regional guidelines use slightly different cutoffs. BMI is commonly employed as a quick screening tool in clinical practice and public health to estimate whether a person’s body weight may be associated with health risks.

For children and adolescents, BMI is interpreted using age- and sex-specific percentile charts or z-scores. Typical cutoffs are underweight below the 5th percentile, normal weight 5th to 85th percentile, overweight 85th to 95th percentile, and obesity at or above the 95th percentile.

Limitations of BMI include that it does not measure body fat directly and does not distinguish between fat and lean mass. Individuals with high muscle mass may have a high BMI without excess body fat. It also does not reflect fat distribution and may be less accurate for older adults, pregnant individuals, or certain ethnic groups. Therefore BMI is often supplemented with additional measures such as waist circumference or body-fat assessments.

Historically, the concept was introduced by Adolphe Quetelet in the 19th century, and the term BMI was popularized in the 1970s by researchers including Ancel Keys. It remains a widely used, inexpensive screening tool for population health and clinical assessment.