Body Mass Index (BMI) represents an index of body weight in relation to height. While BMI is not a measure of body fat, it is recommended as a more accurate way to assess body fatness than measuring weight alone.

In general, people with BMI in Normal range have the lowest health risks.

However, higher BMI does not always mean that a person has too much fat. Although BMI correlates with body fat level, it is not the perfect tool for evaluating the health risks associated with obesity. For example, athletes may have BMI which is higher than Normal because they have more muscle and thus weigh more than average people. But despite their high BMI, they are fit and in good health.

At the same time, BMI which is lower than Normal is usually associated with either extreme natural leanness or, in a worse case, with malnutrition or even starvation.