A buddy and I recently had a brief conversation about the legitimacy of height-weight ratios in assessing one’s health, and specifically, the body mass index (BMI). He’d resumed a workout program several weeks ago, and his doctor gave him a goal weight based on his height and build, although insurance companies – who typically use the BMI – would still consider him overweight or obese. [Calculate yours here.]
This is one major problem with the BMI - like many metrics of any field of study or industry, it’s only a part of the picture. Insurance companies look at height-weight ratios like the BMI because they provide an indication of one’s health risk, since we know that excess weight is associated with various diseases and conditions. While insurance companies also look at other metrics, such as blood pressure and cholesterol, to my knowledge they typically (still) don’t ask for body composition. That is, the percent of one’s body weight that is comprised of body fat. Ultimately, that’s what insurance companies use the BMI for, but by its very nature it can’t give that information. It’s only a height-weight ratio…
Which leads to the other major problem with the BMI – it’s designed for the “average” person. Measure any athlete, whether high school, college, professional, or even recreational, and there’s a good chance that the person is going to show up as overweight or obese according to the BMI. This can even apply to individuals who simply exercise regularly for their own sake, and not for competition. So two people of the same height and weight could have the same BMI value, but very different body fat percentages. Which means that my buddy can shed some fat and add some muscle to get his body fat percentage into a healthy range, and yet he could still face higher premiums due to insurers’ use of the BMI.
In the next post I’ll discuss how I think BMI can be helpful, and why I think critics who decry the legitimacy of the obesity epidemic are wrong.
Very informative, thanks!