BMI not a good measure of body weight
Body Mass Index, or BMI, is often cited when determining if someone is at a “healthy” body weight. But researchers from the University of Pennsylvania have published an article in the journal Science pointing out the problems with using BMI as a means to measure body weight. One of the main factors is that it does not really evaluate body type – it does not take into account fat, fat distribution or muscle mass that may be increasing a person’s body weight.
BMI is calculated by dividing a person’s weight in kilograms by their height in meters, squared. The resulting figure is compared to a chart, where scores of 18.5 to 24.9 is considered normal, 25 to 29.9 is overweight, and a BMI over 30 is obese. BMI was developed in first half of the 1800s, and is often criticized for its inability to reflect the changing nature of people’s bodies. As mentioned, the authors of this report are critical of the measurement due to its inability to evaluate fat versus muscle, bone structure or differences in race, gender or age.
So why is it used so often? Because it’s simple and can provide a reasonable measure of body fat. But it’s not truly accurate, says Dr. Rexford Ahima, the article’s author. She argues that no single number can represent a healthy weight because it depends on starting weight, genetics, gender and numerous other factors.