BMI: Obesity-Detecting Bullet or Bunk?

The Body Mass Index, or BMI, is a crude measure of fatness in individuals. Calculated by dividing one’s weight in kilograms by the square of one’s height in meters, it has been the standard determination of fatness and fitness in doctor’s offices, insurance companies and for governmental statisticians since the 1970s. It has been touted as a measure not just of one’s fatness, but also their health. But is this really true?

BMI: Never meant for individuals

The BMI was created in the 19th century by a Belgian statistician who was trying to assess the collective weight of a population. It was never created for, nor intended to be used, on individuals. However, the ease of the formula made it more convenient for doctors and insurance companies to use rather than more complex measures of fatness such as skin-fold caliper testing or underwater weight displacement testing, so it became the norm.

BMI: Does not make a distinction between lean muscle and body fat

BMI is only concerned with weight and height and thus does not distinguish between all the parts that influence body weight. Thus, someone could be very muscular or simply holding excess water, but have very little body fat, and be considered “obese” according to the BMI. Technically “obese” means having an excess of fat, so if BMI does not make a distinction between muscle, bone, fat or water, then it can not accurately measure one’s fatness, nor their fitness. Example, according to his BMI, a six-foot, 250-pound man will be obese, but if he were an NFL lineman of 6-foot-3 weighing 280 pounds, he might be solid muscle with only 2 percent body fat. According to their reported BMIs, actors Tom Cruise, Mel Gibson and Sylvester Stallone are technically “obese.”

Men only

The BMI was created from research on male populations. An entirely different formula was originally used for determining obesity in female populations, and yet, doctors use the same equation for both genders.

Another way to health without focusing on weight

The Health At Every Size® approach recognizes the inherent failings in the current paradigm of focusing on weight (and BMI) to address issues of mortality/morbidity and thus seeks to change the conversation and clinical intervention to one of health promotion, irrespective of weight.