What are the limitations of the body mass index (BMI) assessment?

The body mass index is merely a ratio of weight to height.  Therefore, it does not take body composition into account.  This means that this assessment does not account for whether your weight is predominantly fat or muscle.  It is possible to be very fit and muscular and be considered “overweight” based on your BMI.  However, for the general public, body composition is a fairly accurate estimate of whether or not you fall into a healthy weight range.

BMI is an index of a person's weight in relation to height. BMI is a very useful and accurate tool for screening the general population to determine increased health risks associated with excessive body weight. One limitation to the body mass index is that it does not differentiate between fat and lean body mass. For example, an athlete or bodybuilder with a large amount of muscle mass could very easily fall into the overweight or obese categories based on their BMI. However, BMI has been found to be very consistent amongst the general population.