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The study, which was recently published in the Journal of the American Medical Association, reviewed more than 100 previously published research papers about the link between body weight and mortality risk for nearly 3 million participants. Not surprisingly, obese people had an increased risk of death during the course of the study. But interestingly, overweight (but not obese) individuals had a 6% decreased risk of mortality when compared to their so-called “normal weight” counterparts. The findings held true despite gender, smoking status and region of the world.
With more than 2/3 of Americans overweight, the term “normal weight” is actually a bit misleading. The study used body mass index (BMI) categories set by the Word Health Organization as follows:
- Underweight = BMI less than 18.
- Normal weight = BMI between 18.5 and 25
- Overweight = BMI between 25 and 30
- Obese = BMI of over 30
The findings aren’t really new, but many people continue to be surprised by the data. Most people don’t expect to find a benefit associated with being overweight, so what’s the real story? Why might overweight people actually live longer?
There are a few theories.
For one, overweight people may get better medical care because they’re either screened more regularly or already seeking treatment for an ailment. This added medical care might give overweight individuals a leg up on their thinner counterparts.
Alternatively, the researchers believe there may be a high chance for overweight people to survive medical emergencies. For example, if you get sick and lose 20 pounds, it helps to have the extra 20 pounds to lose.
Or it could be that the thin people are thin because they’re already sick. It could basically be a case of reverse causation. Perhaps being thin doesn’t make you sick, but being sick makes you thin.
Moreover, the study doesn’t look at quality of life or how healthy thin vs. overweight individuals were at the time of death.
The study certainly isn’t a free pass to gain some extra weight or to eat an extra scoop of ice cream. Instead, it shows us how complicated the link is between our weight, our health and our longevity.