The End of BMI? Know Your Maximum Weight Limit

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Most consumers are familiar with body mass index, or BMI, which refers to how much body fat you hold on your frame versus the amount of muscle and bone. For years, scientists have been using a complicated formulation which involves calculating your own body weight multiplied by 703, divided by height in inches squared -- and then online calculators are supposed to show a "healthy weight range." Whew!

Here's an example using me: I am a 5-foot 6-inch "healthy" active person. I plug in my numbers to any online BMI chart and out pops my "healthy range" which means if I weigh between 120 and 150 pounds (which I do, on the low end), then my "healthy weight range" of 120 to 150 pounds should have a BMI between 19 and 24. OK, but what exactly does it mean?

For years, fitness experts have been considering re-jiggering the BMI formulations to reflect your Fat Mass Index (FMI) instead, which is the number we're truly interested in and the number that pertains to diseases such as diabetes and obesity. In fact, scientist Thomas Kelly of Hologic Inc. in Bedford, Mass. and colleagues recently revealed new body fat composition measures as part of the CDC's National Health and Nutrition Examination Survey. Kelly and colleagues suggested FMI could eventually replace BMI as a more accurate indicator of excess body fat and, therefore, of obesity-related health risks.

One researcher, however, has set out to create a simpler way of calculating BMI, and one that wouldn't require charts or online calculators. George Fernandez, a professor of applied statistics and director of the Center for Research Design and Analysis at the University of Nevada, Reno, releases his findings today at the Nevada Public Health Association Conference at the University of Nevada. He's calling it Maximum Weight Limit, rather than BMI.

"It's a simple calculation that most of us can do in our heads," he says in a press release. For men and women, there is still a baseline height and weight. For men, the baseline is 5-feet, 9-inches tall and a MWL of 175 pounds, meaning that a 5-foot, 9-inch tall man should weigh no more than 175 pounds. For women, the baseline is 5-feet tall and a MWL of 125 pounds.

"These are nice round numbers that people can remember," says Fernandez. Then, if you are a man, add or subtract 5 pounds for every inch you are taller or shorter than 5 feet, 9 inches. So, if you are 5-feet, 11-inches tall, you are 2 inches taller than the baseline. You add 5 pounds for each of those 2 inches over the baseline, 10 pounds in this case. So, your MWL is 185. Women add or subtract 4.5 pounds for each inch they differ from the baseline height of 5-feet tall.

To start figuring it out for yourself, check out this information on BMI.