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So you know how we’re always being told that fat people need to lose weight to be healthy? Yeah, that’s something we should probably take a closer look at, because it turns out it’s based on what “everybody knows” and hypothesis rather than research. We can start with the work of Traci Mann and A. Janet Tomiyama. In 2007, they reviewed studies of long-term effects of dieting and found that:
“These studies show that one-third to two-thirds of dieters regain more weight than they lost on their diets...the studies do not provide consistent evidence that dieting results in significant health improvements, regardless of weight change. In sum, there is little support for the notion that diets lead to lasting weight loss or health benefits.”
That hasn’t changed -- there isn’t even one study where more than a tiny fraction of participants maintained their weight loss in the long term. Mann and Tomiyama have just released another study review about the relationship between weight loss and health.
“We uncovered no clear relationship between weight loss and health outcomes related to hypertension, diabetes, or cholesterol, calling into question whether weight change per se had any causal role in the few effects of the diets. Increased exercise, healthier eating, engagement with the health-care system, and social support may have played a role instead.”
Which is to say that changing body size does not automatically create better health, which shouldn’t be a big shock since there are healthy fat people and unhealthy thin people. Health is not entirely within our control and there are no guarantees, but the research is clear that behaviors are a better indicator of future health than body size. If that sounds different than what you’ve heard it’s because this research doesn’t get any attention.
Recently there was a media storm around research that found that fat people died sooner than thin people even if those fat people had good metabolic numbers. Almost none of the coverage mentioned that the studies didn’t have a control for behaviors which was pretty strange since previous research had shown that behaviors mitigated the risk for earlier death.
Mann and Tomiyama’s study, though better designed, has received only a fraction of the attention. I call this a Galileo issue…like the idea that the sun revolved around the Earth, the idea that anyone who tries hard enough can lose weight and that weight loss will lead to better health is widely believed, fervently supported, and heresy to question.
But, just like Galileo’s house arrest didn’t change the fact that the sun does not revolve around the Earth, shouting down people discussing the research around weight and health doesn’t change what that research says. Our best chance for our healthiest body is to participate in healthy behaviors and let our body size settle where it will, not to attempt to manipulate our body size though food and exercise in the hopes that it will somehow create health.