Overweight is measured by means of the body mass index (BMI). The BMI is defined as the body weight in kilograms divided by the height in metres squared. A BMI exceeding 25 is an indication of overweight. An index ranging between 25 and 30 indicates moderate overweight and an index exceeding 30 indicates obesity.

Respondents of the Health module of the Integrated System of Social Surveys (POLS) were invited to report their body weight and height and subsequently their BMIs were calculated. The figures are based on a sample and therefore subject to a margin of error.