Yo-Yo Dieting: A Seductive Mix of Myth and Reality

Yo-yo dieting is an boogeyman that persists stubbornly in defiance of the facts. A recent study published in the New England Journal of Medicine is the latest fuel for a mix of derision and fear mongering. Researchers found an association between weight fluctuations and bad outcomes from heart disease.

They did not study dieting or yo-yo diets. Just weight histories and heart disease outcomes.

But still, NPR decided that the headline should be: “Yo-Yo Dieting May Pose Serious Risks for Heart Patients.” And NPR was not alone in its fear mongering.

What Is Yo-Yo Dieting?

Yo-yo dieting is a derisive term that can mean whatever you want. Anytime someone loses weight, regaining some of that weight is inevitable. All of it might come back. Yo-yo dieting is also called weight cycling and typically refers to repeated cycles of losing, regaining, and then again losing weight through a restrictive diet.

The idea that weight cycling will “ruin your metabolism” or “kill you” comes from observational studies that associate fluctuations in weight with bad health outcomes. Like any seductive presumption it blends a grain of truth with a vivid narrative.

The grain of truth comes from metabolic adaptation. When people intentionally lose weight, their bodies adapt to try to gain it back. Metabolism slows down. The brain starts tuning in to cues for food. Hunger increases. This is all absolutely normal.

The other grain of truth is that temporary changes in diet – by themselves – are an utter waste of time. The idea that you can simply lose some weight, resume an unhealthful lifestyle, and stay at a lower weight is pure fiction. Dietary changes only work over time if they are sustainable. The Mediterranean diet is an example of something that tends to work. Countless others are more faddish and likely burn out.

The Problems with Yo-Yo Dieting Folklore

The seductive folklore of dieting dangers has two problems.

The first problem is that the concept easily becomes a weapon. It provides a tool for making people feel stupid or bad if they regain weight they’ve lost. It can have the effect of telling people to forget it. They’re doomed.

The second problem is that it’s a giant leap from correlation to causation. All the studies – including this latest one from NEJM – are observational. People lose and gain weight for many reasons, not just dieting. Often the reason for weight loss is illness. Those observational studies can’t prove a cause and effect relationship with intentional weight loss. And they don’t justify discouraging people from trying to lose and maintain a healthier weight.

A Better Frame of Reference

Clearly, quick fixes for excess weight and obesity are rare or nonexistent. Short-term diets without a long-term plan for a healthy lifestyle are a waste.

But real, lasting changes in dietary habits can make a real difference for life and health. Do it yourself. Or better yet, do it with smart coaching from a dietitian.

Just do it with your long-term goals in mind.

Click here for the study in NEJM and here for reporting from NPR. For a thoughtful analysis  of this and other common, unproven beliefs, click here.

Yo-Yo! Photograph © Miguel / flickr

Subscribe by email to follow the accumulating evidence and observations that shape our view of health, obesity, and policy.

May 4, 2017