The Truth About Yo-Yo Dieting and Your Metabolism

We all know about the perils of yo-yo dieting--by repeatedly losing weight then gaining it back, you end up trashing your metabolism and making it harder to lose weight and keep it off the next time around.

Or do you? This is one of those classic cases of knowledge by correlation: if you sample a large group of people, the ones with a history of weight cycling will tend to have higher weight and poorer metabolic profiles. But that doesn't really establish causation. What if the people with poor metabolic profiles are most likely to struggle to keep weight off throughout their lives, predisposing them to weight cycling? Researchers from Fred Hutchinson Cancer Center decided to reanalyze data from a big weight loss study to see if a history of weight cycling prospectively affected the changes in weight and metabolism after 12 months. The results were published recently in the journal Metabolism.

Related: Top 6 Reasons Your Weight Loss Plan Isn't Working

The results were (as you can probably guess from the fact that I'm blogging about them) surprising: there were basically no differences in the changes seen by non-weight-cyclers, moderate cyclers (reported losing at least 10 pounds at least three times), and severe cyclers (reported losing at least 20 pounds at least three times). That includes weight loss, percentage of fat versus muscle gained or lost, blood pressure, insulin sensitivity, and appetite-linked hormones like leptin. (Plus: Running vs. Walking for Weight Loss: Read our debate on which workout actually burns more calories.)

Now, there are all sorts of caveats here. Just because this study didn't find any negative effects from weight cycling doesn't mean there aren't any. And of course, nobody actually recommends yo-yo dieting. But this does play into a rather important debate about whether people who are overweight should attempt weight loss. Given that cardiovascular fitness seems to be a better predictor of health than BMI, some experts suggest that deliberately trying to lose weight might be a bad idea unless medically indicated, given the potential for damaging your metabolism. But before we adopt that viewpoint, it's worth asking: which is the cause, and which is the effect?

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Stop yo-yo dieting and slim down for good--follow these 10 Tips for Weight Loss That Lasts.

--By Alex Hutchinson

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