Cycling in Italy

Science vs Fervent Beliefs About Weight Cycling

Dieting has a bad reputation these days. In popular culture, the concept has lots of detractors. Instead of “going on a diet,” it’s more fashionable to say, “I’m eating healthy.” The reasons for  this shift in attitudes are many. For one thing, a sustainable, healthy pattern of eating seems to be a better way to maintain a healthy weight. Diet-related health outcomes are better when you find a pattern for eating you can maintain. But one of the reasons dieting gets a bad rap isn’t holding up too well under scientific scrutiny. And that’s weight cycling. Also known as yo-yo dieting.

A new mouse study, published in Obesity today, offers good reasons to question the presumption that weight cycling itself causes physical harm.

Does It Really Wreck Your Metabolic Health?

It’s an article of faith within the Health at Every Size movement. Weight cycling is a dire threat to health. Part of the concern is the psychological impact. But another part of the suspected problem is an effect on physical and metabolic health. Observational studies have created the impression that weight cycling leads to bad health outcomes.

However, a careful review of the evidence for the effects of weight cycling finds “sparse evidence” for an effect on morbidity and mortality. Prospective human studies would be difficult, if not impossible. So this new study in mice is actually quite valuable.

With funding from NIH, Daniel Smith and colleagues conducted a randomized, controlled trial. They compared the effects keeping mice in a state of obesity to having them go through multiple cycles of losing and regaining weight. A third group lost a modest amount of weight and maintained that lower weight.

A Surprising Finding

It turns out that repeated weight cycling actually led to mice living longer than mice who stayed in a state of obesity. In fact, the survival benefit was similar, regardless of whether a mouse maintained a lower weight or experienced cycles of weight loss and regain. The authors commented:

To the extent to which these findings represent those that might occur in humans, our results suggest that persons with obesity may benefit from weight loss in terms of longevity, even if the lost weight is regained and the loss-gain cycle is repeated multiple times. If so, perhaps weight loss is not so ill-fated a resolution after all.

Of course, we’ll be the first to say that mice and people are very different. This is not evidence that weight cycling is a good thing for human health. For one thing, the psychological effects of weight cycling are important. Feelings of futility and failure come along when people regain weight they’ve worked hard to lose.

But here’s something to consider. It’s worth thinking about the possibility that dire warnings about weight cycling might make people feel worse about themselves when they experience it. Maybe fervent beliefs about weight can be a cause of harm. Especially when they’re imposed upon others.

Click here for the study in Obesity. (Please be patient if the link is not yet active.)

Cycling in Italy, photograph © will_cyclist / flickr

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October 24, 2018