BMI Not an Accurate Assessment

For years doctors have been using BMI calculations to assess whether or not someone is a healthy weight, however, recent research shows that the body mass index; based on height and weight, is not an accurate measurement for body fat content and doesn’t account for important factors that contribute towards health or mortality. Issues such as fat distribution, proportion of muscle to fat, gender and racial differences in body composition are not measured when calculating a person’s BMI.

BMI, devised between 1830 and 1850, is calculated by dividing a person’s weight in pounds by their height in inches squared, then multiplying the answer by 703. A person is underweight if their BMI is below 18.5, normal if their BMI is between 18.5 and 24.9, overweight if it is between 25- 29.9 and obese if it is 30 and above.

Many experts argue that as muscle weighs more than fat, BMI is not helpful in assessing athletes who weigh more due to muscles. A study at Michigan State University examined the BMI results of athletes and found that two thirds of male athletes and one third of female athletes fell into the overweight category.

Dr. Ahima, a researcher from a recent study done on BMI in the University of Pennsylvania, said that, “There is an urgent need for accurate, practical and affordable tools to measure fat and skeletal muscle […] that can better predict the risks of diseases and mortality […] taking into account factors such as age, sex, genetics, fitness, pre-existing diseases.”

According to Dr. Ahima, a major flaw of BMI is that it doesn’t specify the location of fat. Research has shown that excess fat around the abdomen increases the risk of diabetes and heart disease. This abdominal fat, called visceral fat, is stored around the internal organs and is more harmful than fat simply sitting under the skin. Even slim people can have high levels of visceral fat but still have a low BMI and be considered healthy when they might be at risk of developing health problems. One way of overcoming this BMI problem is by measuring the waist with a measuring tape lined up above the top of the hip bone. A healthy waist is less than 37” for a man and less than 32” for a woman.

Paul Gately, professor of exercise and obesity at Leeds Metropolitan University, advises that, “If a person feels they’re fit and is surprised by a BMI reading, they should have a body composition analysis.” This is most easily done with a high-tech weighing scales that passes an electric current through the body and determines proportional body make-up by passing through fat, muscle and bone at different speeds.

Fiona McBennett