The Body Mass Index, which may soon be required by the Equal Employment Opportunity Commission to impact company health premiums among other things, is ridiculously simplistic measure of health. How much you weigh vs. how tall you are, taking nothing else to account, is used as a proxy of your health.

A study out of UCLA explains why that’s a rather unhealthy approach:

The scientists analyzed the link between BMI — which is calculated by dividing a person’s weight in kilograms by the square of the person’s height in meters — and several health markers, including blood pressure and glucose, cholesterol and triglyceride levels, using data from the most recent National Health and Nutrition Examination Survey.

The study found that close to half of Americans who are considered “overweight” by virtue of their BMIs (47.4 percent, or 34.4 million people) are healthy, as are 19.8 million who are considered “obese.”

Given their health readings other than BMI, the people in both of those groups would be unlikely to incur higher medical expenses, and it would be unfair to charge them more for health care premiums, Tomiyama said.