PolySciFi Blog

Thursday, April 21, 2005


BMI, Weight, and Health

A study revealed that if you're a little "overweight," it's good for your health.
"People who are a little overweight are likely to live longer than people who are underweight or obese, a study shows....

BMI of 18.5 to 25 is considered normal. One below 18.5 is considered underweight and 30 or above is considered obese. The researchers found that the people who had BMIs higher than 25 but lower than 30, which meant they were moderately overweight but not obese, did not have a reduced life expectancy.

The people who lived the longest of all were those with BMIs of 25, which lies between the ideal and overweight margins."
I have a different explanation - BMI is a lousy indicator for when someone is fat. Too much fat in your body is what's really bad for you, not your weight. Muscle simply weighs more than fat and being in good anaerobic shape (which is usually accompanied by being in good aerobic shape) automatically makes you overweight by BMI. When BMI indicates that half of the players in the NBA are overweight, there's something wrong with the application of BMI. [when did we become the NBA blog and not the beer blog? -ed The playoffs are coming up and I got too busy to drink...] When BMI fails to predict health (see above), then there's something wrong with the application of BMI.

A far better measure for being unhealthy due to weight is a hihgh body fat percentage for which BMI is a crude measure.

My suggestion: all BMI studies should be taken with a grain of salt, and for your own personal health calcualtions, use a scale that measures body fat, like this one.

As a partial defense of BMI (the inability to differentiate between muscle and fat remains), I wonder if this study was affected by the NIH's 1998 recalibration of an overweight BMI from 27 to 25. This had the effect of reclassifying 30 million Americans as "overweight" who were previously "ideal weight." Perhaps the original classification was correct.


This page is powered by Blogger. Isn't yours?