Friday, July 12, 2013

The obesity paradox - fat people may live longer!

Virginia Hughes writes about accumulating data on obesity and longevity that many researchers wish would just go away, after all the effort that has been put into documenting the health risks that go with obesity. At issue, for example, is a meta-analysis, lead by Katherine Flegal, of 97 studies including 2.88 million people that reported people deemed 'overweight' by international standards to be 6% less likely to die than were those of 'normal' weight over the same time period. There has been furious debate over this result because the epidemiology involved is complex, and eliminating confounding factors is difficult. However,
....many researchers accept Flegal's results and see them as just the latest report illustrating what is known as the obesity paradox. Being overweight increases a person's risk of diabetes, heart disease, cancer and many other chronic illnesses. But these studies suggest that for some people — particularly those who are middle-aged or older, or already sick — a bit of extra weight is not particularly harmful, and may even be helpful. (Being so overweight as to be classed obese, however, is almost always associated with poor health outcomes.)  Click on graphic to enlarge:

...the most contentious part of the debate is not about the science per se, but how to talk about it. Public-health experts, including Willett, have spent decades emphasizing the risks of carrying excess weight. Studies such as Flegal's are dangerous, Willett says, because they could confuse the public and doctors, and undermine public policies to curb rising obesity rates. “There is going to be some percentage of physicians who will not counsel an overweight patient because of this,” he says. Worse, he says, these findings can be hijacked by powerful special-interest groups, such as the soft-drink and food lobbies, to influence policy-makers.
But many scientists say that they are uncomfortable with the idea of hiding or dismissing data — especially findings that have been replicated in many studies — for the sake of a simpler message. “One study may not necessarily tell you the truth, but a bulk of studies saying the same thing and being consistent, that really is reinforcing,” says Samuel Klein, a physician and obesity expert at Washington University in St Louis, Missouri. “We need to follow the data just like the yellow brick road, to the truth.”


  1. I think the question is what is "a bit of extra weight" vs. obesity. If the message has been the only way to be healthy is to have no body fat, that's been going too far.

  2. Martha1:26 PM

    BMI is based on a height-weight ratio, and we all loose height with age. Wonder how this affects the studies? Also, wonder if body composition influences longevity; something BMI doesn't measure. And, as we get older we get sicker unfortunately. Weight loss in older people may be the result of either diagnosed or undiagnosed disease. All this makes the finding less clear cut than it at first glance seems.

  3. totally agree with martha.