Sloth Awakens

Should We Shift Our Thinking About Metabolic Adaptation?

You’ve probably heard that dieting can wreck your metabolism. It’s a simple way to explain repeated cycles of losing and regaining weight. But it’s a pretty poor explanation for the complexity of metabolic adaptation. A new study in Obesity asks us to consider an alternate view.

Calorie Restriction or Overfeeding?

It’s true enough that when you restrict the calories you consume and start losing weight, your body will start to adapt. Metabolic rate will slow down. You body gets more efficient and uses fewer calories to get by. Over time, that pushes you back toward your starting weight. Sometimes people regain more than they lost. But it’s not clear that you can blame incremental weight gain on having once lost weight.

Seth Creasy and colleagues ask us to consider a different way of looking at metabolic adaptation. How do we respond to overfeeding?

They studied a small group of people identified as either obesity resistant or obesity prone. They put them into a controlled environment, measuring everything they did and ate. For three days, they fed the subjects exactly 100% of their bodies’ energy needs. Then for three days, they overfed them with 140% of energy needs.

Afterward, the researchers let the subjects eat and do whatever they wanted, while monitoring them closely for three more days. In the five years that followed, Creasy et al measured each subject’s weight and body composition annually.

What they found was that individuals resistant to obesity became more active in response to overfeeding. But people prone to obesity did just the opposite. They became more sedentary. And over time, the people who became more sedentary after overfeeding were the ones who gained weight.

An Opportunity to Refocus

Typically when we think about metabolic adaptation, we think about the response to eating less. But in fact, we’re living in a food environment that constantly pushes more food at us than we need. “Would you like fries with that?” It might be that adapting to overfeeding is the more important metabolic response to understand.

Creasy gives us some good reasons to think so.

Click here for the study and here for further perspective from Michael Rosenbaum.

The Sloth Awakens, photograph © Tim Evanson / flickr

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April 23, 2018