Naysayers decry the fallibility of BMI measurements as an accurate representation of “ideal” weight. There are many arguments against the use of BMI, such as the fact that it doesn’t consider body type, or the fact that it doesn’t consider body fat percentage. Despite the arguments, the real question that must be answered is if, and what, the value of BMI may be, as it relates to health.
The Health Risks Of A High BMI
A recently released study, published in the New England Journal of Medicine, examined the merit of the BMI measurement, as it relates to risk of death, from all causes. Conducted as a meta-analysis, the authors examined the results of 19 studies, adjusting for variables such as age, marital status, etc. The results were striking.
Let’s start with a primer on how to calculate BMI:
- Multiply your weight (in pounds) by 703
- Divide the answer from Step #1 by your height (in inches)
- Divide the answer from Step #2 by your height (in inches)
The National Institute of Health categorizes BMI values as follows:
With that backdrop, authors of the study reported that across a broad swathe of a non-Hispanic Caucasian populace, which included approximately 1.46 million people, those individuals who had never smoked and had no history of cancer of heart disease, and had BMI’s ranging from 20-24.9 had the overall lowest risk of death from all causes.
Perhaps not suprisingly, those individuals having BMI’s between 30-34.9 were at a 44% greater risk of death those having a more “ideal” BMI. People having a BMI of 35-39.9 were at an 88% increased risk of death, from all causes.
OK. So I know the response from the bodybuilding crowd, which contends that BMI only considers mass, and not percentage body fat or frame size. However, for all its faults, it provides a single value for defining an “ideal” range. It’s also true that, regardless of whether one is carrying a large quantity of fat or muscle, in both cases, the heart must support that excess tissue, which increases the workload.
The same principle is at work with professional cyclists. Research has shown that many professional cyclists have an enlarge heart. While these people are, without a doubt, some of the fittest people in the world, by virtue of overtraining, they can develop a health risk.
Too much of a good thing?
I may get some people going with this one. And, I fully understand the sentiment. BMI is, without a doubt, an oversimplification. But, its also impossible to ignore the fact that, overall, BMI is a good indicator of the impact of your weight on overall health. So, in my mind, if my BMI and percentage body fat each fall withing the recommended guidelines, I figure I’m doing OK.