BMI in NJEM – orly?

December 3rd, 2010  |  Published in Stumpblog  |  8 Comments

A new metastudy in the NJEM, which pooled data from 19 long-term studies looking at deaths from any cause found that a body mass index (BMI) between 20.0 and 24.9 is associated with the lowest risk of death in healthy non-smoking adults.

Previous studies weren’t able to predict specific health risks from being overweight/obese; this new study provides precise estimates of the increased risk of death among people who are overweight and obese, and exactly how much one’s risk appears to increase depending on BMI.

Currently, two-thirds of U.S. adults are overweight or obese. 17 percent of women are severely obese.

Healthy women who had never smoked and who were overweight were 13 percent more likely to die during the study follow-up period than those with a BMI between 22.5 and 24.9. Women categorized as obese or severely obese had a dramatically higher risk of death.

One thing to note here is that one needn’t be skinny/lean/Ms Sixpack-Abs to see improved health.

You can easily and dramatically improve your health outcomes simply by getting BMI in the “normal” or even slightly overweight ballpark as a result of good nutrition and regular activity. If you’re fit and your BMI is in a decent range, you can rest easy. If you’re unfit and that BMI is creeping up… you take your chances.

Responses

  1. Jess says:

    December 3rd, 2010at 9:14 pm(#)

    I am a little surprised to see this study posted here, given that one of the surest ways to get a BMI in the overweight or obese range is to take up weightlifting. BMI doesn’t distinguish between muscle weight and fat weight, which makes it a terrible index of healthfulness… pretty much all of my weightlifting friends mock BMI mercilessly for classifying them as obese when they’re really just densely muscled.

  2. Mistress Krista says:

    December 4th, 2010at 4:22 pm(#)

    @Jess: As someone who has now worked with hundreds of clients in great detail (including very close measurement of body weights, girths, and fat %) I can say that very few fit folks whose body fat is in a healthy range truly do have an overweight/obese BMI from muscle. It is rarer than folks expect. It’s not uncommon to be at the edge of the “overweight” BMI, but it’s extremely rare to have an “obese” BMI and be extremely fit and muscular with an appropriate level of body fat. It is, however, common for folks to overlook the fact that their body fat is higher than it should be (and again I don’t mean sixpack abs, I mean “normal healthy” range, even a bit squishy).

  3. Ginny says:

    December 6th, 2010at 2:04 am(#)

    I expect it to be especially uncommon for women. I would need to add something like sixty pounds of muscle to be simultaneously lean and obese. I doubt if that is possible by any natural means (if only!).

  4. Belatrix says:

    December 6th, 2010at 10:25 am(#)

    I’m not so sure about this BMI thing. I’m hovering just on the edge of the overweight category. Some days I’m a little over, some days I’m a little under. However, I can see the top two rows of my abs and some nice muscle definition when I flex something. I’m not really serious about weight lifting, if I was I could see myself gaining a little more muscle and thus weight.

  5. coach_andrew says:

    December 8th, 2010at 8:18 am(#)

    i dismissed the value of BMI for years in re heavily built larger athletes [back when i was one] until someone framed it differently for me– think of BMI as an indicator of the systemic load upon the heart, regardless of body comp.
    look at the report above– women with a BMI indicating that they were overwiegh/ obese were 13% MORE LIKELY TO DIE than those BMI lesser than 24.9
    and note the closing ling: “If you’re fit and your BMI is in a decent range, you can rest easy. If you’re unfit and that BMI is creeping up… you take your chances.”
    don’t shoot the messenger

  6. Mistress Krista says:

    December 8th, 2010at 8:27 am(#)

    @coach_andrew: Great point here. We have to consider a variety of factors that increase risk including the chemical environment created by body fat (which is an active endocrine — aka hormone-secreting — system) as well as the mechanical loading of body weight. I came across a study some time ago indicating that heavyweight NFL football players had a significantly elevated risk of cardiovascular events despite their relatively elite levels of fitness. Many heavyweight powerlifters have drawn the same conclusions.

    Everything is about trade-offs and compromise, and physiology is all about the “sweet spots”. A bit more weight — if it’s frequently-used lean mass (including dense bones) — is generally good metabolically and mechanically. Past a certain point, though, the trade-offs change.

    Folks get all-or-nothing about this and assume that if a high BMI is not so great, we’re saying that the lower the BMI the better. This is definitely NOT true. Again, sweet spot.

  7. Fiona says:

    December 8th, 2010at 4:03 pm(#)

    @Belatrix: The way I read that study, it looks like they’ve validated the correlation between BMI and early death, except that the original “healthy” was off by a point or two – people just above the old “healthy” are as likely to die as people just above the old “underweight”… so the new “healthy” should be 20-25 or 18.5 to 30, instead of 18.5 – 25.

    Of course, different people are different and you, as somebody who works out, are probably healthier than somebody who’s dieted herself down to 20… but there seems to be a pretty clear correlation.

  8. Terry Gibbs says:

    December 8th, 2010at 7:33 pm(#)

    Andrew Krista, very nice. Agree that BMI is misleading, but know lots of people who are 50lbs overweight (fat) who looking in the mirror, think if I just lost 15lbs I would be ripped.

    I was happily supplementing my diet with choclate ( it was the vegetarian in me) happily content, that any extra weight would help my masters throwing (I throw 56 and 100lbers) . logic worked until I met Koji Murofushi – 2004 Oly games hammer champ. Koji told me that he had his second best ever throw at only 94kg. sigh ….hard to justify the love handles any more..

    older I get the more I realise it is all about balance.


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