Surprising New Findings on Obesity

One of the first Freakonomics Radio podcasts we made was an episode about the (surprisingly tenuous) link between obesity and health problems. A new study in The Journal of the American Medical Association finds that “Grade 1 obesity overall was not associated with higher mortality, and overweight was associated with significantly lower all-cause mortality.”  Writing for The Daily Beast, Kent Sepkowitz explains:

Compared to people with a normal weight (a BMI less than 25), the overweight (BMI between 25 to 30) had a 6 percent lower mortality rate—and both groups had a rate about 15 percent lower than the obese, especially the very obese (BMI above 35).

The explanation for the finding is uncertain. Perhaps the pleasantly plump but not obese have an extra reserve—a literal spare tire—that confers a survival advantage should they become seriously ill, whereas the lean-iacs do not. Or maybe the thin ones were thin because of a serious illness that, in the course the various studies, killed them. Or maybe the thin ones were thin because they were chain smokers living off Scotch and potato chips. Or just maybe the occasional pig-out does soothe the soul and make for a happier, healthier individual.

(HT: Andrew Sullivan)

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  1. Ned Cody says:

    There’s something dodgy about the mathematics, I think. How can mortality rates which differ by 6% both be equally below another mortality rate? And the cut-off values must be deceptive: how can a grouping of 29.8 bmi-ers be 15% less likely to die than a group of 30.0 bmi-ers.
    I’m only saying…

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  2. Eric M. Jones. says:

    Fat jiggles to attract attention–signaling breeding fitness.

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  3. TexCIS says:

    Smokers usually weigh less. Reexamine the data excluding them and see what is revealed.

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  4. AaronS says:

    I have a theory. It comes from a lifetime of being the “big guy.” Very simply, I believe that some people are “designed” to carry additional weight. We’ve all seen those folks who, with just a few extra pounds, are huffing and puffing. Or even those folks who, morbidly obese, can barely get around.

    And then we’ve seen folks who, even 50 lbs. overweight, are active, vibrant, etc.

    For many years, I didn’t understand why some people suffer heart attacks before 30, while I, much, much larger than them, enjoyed relatively good health.

    I have concluded that some people have a body, metabolism, or something that simply permits them to successfully carry more weight. I’m not saying that’s the best thing. I’m simply saying that IF they have more weight, it doesn’t negatively affect them like it might another person. Perhaps later in life, but at least year-for-year, pound-for-pound, they do much better. No, they won’t be going to the Olympics, but they will be able to enjoy a larger plate of food and desserts than others, all with relatively minimal impact to their health (at least until much later).

    I see some morbidly obese who die in their 50s…then others who are big until true old age. Maybe they don’t live as long, but for those special ones that seemed designed to handle lots of extra weight, it sure seems that they enjoyed life without worrying too much about calories.

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  5. Phoebus Rising says:

    Sounds like Mr. Sullivan might be one of the “pleasantly plump”.

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  6. Matthew V says:

    I also remember seeing a study on BMI that showed various football players. Linemen and running backs (or some other position, don’t like the sport) that had the same BMI, but completely different fitness levels had similar life expectancy. In other words, the fat guys and the fit guys lived to similar ages. Compared apples to oranges and got the same shelf life.

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  7. Rob S says:

    Surprised this hasn’t come up on Freakanomics, but isn’t the mortality rate 100% for everyone?

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    • James says:

      Not yet. It’s only 100% for those who have already died. Saying that it will be 100% (or indeed, any particular number) is predicting the future, which the Freakonomics guys keep telling us is impossible :-)

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      • Eric M. Jones. says:


        Predicting the future for the INDIVIDUAL is impossible. Predicting the certain future for a population is merely statistics.

        That’s why I know that you and everyone else will perish whilst I shall live forever.

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      • James says:

        It’s also possible that science will discover some sort of anti-aging treatment before either of us would kick the bucket (from natural causes, anyway). That would certainly skew the statistics – just as say a major epidemic would skew them in the opposite direction.

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  8. Mira says:

    Did the study take into account how the subjects died? Fit people may be more fit in general because they are more active. But going out and doing things puts you at a higher risk for accidental death than sitting on your couch watching TV…

    Also agree with most here that BMI is far from an ideal way to measure health/fitness. Body fat percentage would probably be a better indicator overall.

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