How Dangerous Is Being Fat? New Data On The Meaning Of Body Mass Index

by Richard Knox
December 1, 2010
NPR

http://www.irishhealth.com/content/image/13886/Obeseman.jpg

If your body mass index is between 20 and 24.9, you're golden.

You won't live forever, but your chances of living longer than those with other BMI values are statistically better, according to an analysis of 1.46 million adults in this week's New England Journal of Medicine. One important proviso: These were Caucasian adults, so if your ethnicity is otherwise you'll have to wait for further research.

(Measure your own BMI with an online calculator like this one.)

Now, to say that people with higher BMIs are more likely to die sooner isn't exactly big news. But it's worth noting because there's been a lot of back-and-forth in recent years about the meaning of BMI. A 2009 advisory from the American Heart Association even suggested that being a little overweight – a BMI of 25 to 30 — might be protective. Others disagreed.

"There was debate over whether having a BMI in the overweight range is associated with an increased risk of death," study author Amy Berrington de Gonzalez of the National Cancer Institute told Shots. "Our study finds that it does. It's a small increase, about 10 percent. But we think it's the best analysis to date."

The reason she thinks so is that it included BMI and mortality data from 19 different studies. Pooling that much data allowed the researchers to exclude people who were smokers or had diagnosed diseases. So they could isolate the effects of BMI.

Berrington and her colleagues calculate that every five-point increase in BMI (for Caucasians in developed countries) leads to a 31-percent increase in risk of death from all causes. (Earlier studies had pretty much nailed down a link between higher BMIs and an increased risk of death from heart disease, stroke and certain cancers — uterine lining, esophageal, pancreatic.)

The study finds that obese people — those with a BMI of 30 to 34.9 — have a 44 percent higher risk of death from any cause compared with those in the most-favorable range. Severely obese people (BMI over 35) have an 88 percent higher death risk. And the most obese (BMI over 40) have a 250 percent higher risk.

These patterns held after the researchers accounted for other risk factors besides smoking and disease, such as alcohol consumption, physical activity and educational level. Those who were overweight or obese before the age of 50 had a higher mortality risk.

These numbers apply to the vast majority of Americans. Two out of every three U.S. adults are overweight or obese. Seventeen percent of women and 11 percent of men are severely obese.

Berrington acknowledges that BMI "is not a perfect measure of body fatness because it can't distinguish body fat from lean mass. But we think it's a valid measure of obesity."

If you want to determine your own BMI, you can multiply your weight in pounds by 702, divide that answer by your height in inches, and then divide that answer again by your height in inches.

Or you can take a shortcut and use the calculator mentioned above.

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Replies to This Discussion

Permalink Reply by T A A on December 6, 2010 at 5:13pm

Yes and Sylvester Stallone and Arnold Schwarzenegger in their prime and many many top athletes are "obese" according to such ridiculous standards! The cheap BMI calculator included in the article does not account for bone size or muscle mass and is essentially useless. It has been proposed by several researchers that our obsession with such cheap self diagnostic tools and methods may play a role in increasing the number of overweight people in our society! It's the theorem of "unforeseen consequences".

The ONLY proper way to calculate BMI is to do a water displacement test and compare the volume to the weight. Calculators give wrong results.

As an example, I weigh between 200-210 lbs and measure 5'6"1/2, YET, when I go diving with friends, I wear the same lead weight as skinny males, 3-4 lbs of lead. I can also easily sink to the bottom of a swimming pool and stay there. I have very large muscle mass and bone mass.

Such studies should be completely disregarded, they are based on faulty foundations.

Permalink Reply by Michael Sizer-Watt on December 24, 2010 at 10:43am

When I was in my 20's I was a competitive natural bodybuilder (those days are wayyy behind me now). I applied for life insurance, the adjuster told me I was obese, so I didn't qualify for the lowest rate of insurance. I told her that I assured her I was not obese (I weighed 165lbs, 5"7, and I don't remember whether I was dieting or trying to gain at that time, but I would have been between 4-6% body fat). She said "I'm sorry sir, but we use the standard BMI calculator, and based on what you're telling me, you are considered obese" (this was over the phone). So I persisted and she finally said "well, we can send a nurse to your home to take blood work and assess you, but if she concludes that you are obese, you will be charged for the cost of the nurse visit. So I agreed. When the nurse finally came, after taking my vitals, she said that I was the fittest person she had ever examined and I ended up qualifying for the highest level of coverage, which apparently is rarely offered unless you pay ridiculous monthly premiums. Today I am much healthier from a mental standpoint, but my body is not a temple but a weather beaten shack. I have to force myself to start doing some exercise again, but I'm just so damn lazy about it now.

Permalink Reply by T A A on December 25, 2010 at 6:19am

Had they done a water displacement assessment of volume on you they would have known that in an instant :)

Chart BMIs are woo, and we atheists should stop looking to them for knowledge.

Permalink Reply by Bill on December 23, 2010 at 9:12pm

I got 24.3 (5"8 X 160), close to overweight, but I sink like a stone...

Permalink Reply by Bill on December 23, 2010 at 10:44pm

I'm pretty happy with my weight, and fortunate to fall within the normal range. It sure takes a lot more work than it did when I was young though!

Permalink Reply by T A A on December 24, 2010 at 6:51am

Yes because chart-based BMIs are BS. I'm a 33 and I sink like a stone, I have huge muscle mass and very dense bones.

Permalink Reply by T A A on December 24, 2010 at 6:28am

I propose that we stop bringing up BMI when it's calculated theoretically! It is a tool which has been demonstrated over and over again to be faulty. Especially when people just pop it out like that without accounting for body type, muscle mass and bone mass.

The only body measurement that is valid is mass:volume, where volume is best assessed by water displacement.

Permalink Reply by T A A on December 24, 2010 at 6:30am

Please do not rely on charts claiming to tell you about BMI, they are inherently faulty. Volume can only be reliably measured by water displacement. Muscly and dense boned people fail all BMI "charts".

Permalink Reply by T A A on December 24, 2010 at 7:02am

You missed the point entirely... CHART based BMIs are BS, the only good BMI is derived from an ACTUAL MEASUREMENT OF VOLUME BY WATER DISPLACEMENT.

Chart based BMIs are no better than homoeotherapy.

Permalink Reply by T A A on December 24, 2010 at 8:00am

woah, mega 4am typo, sorry bout that!

Permalink Reply by T A A on December 24, 2010 at 7:30am

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