An Elusive Reality: Slower Metabolism with Weight Loss

For people who care about the science of obesity and metabolism, this is a fascinating story – still unfolding. For others, it can be a source for cherry-picked factoids. Whatever your pleasure, you can find important insights in a new study published yesterday in Obesity. Catia Martins, Barbara Gower, and Gary Hunter analyzed detailed metabolic data from 65 Black and White premenopausal women. The have data both before and after an average of 16 percent weight loss. What they found was convincing evidence that slower metabolism after weight loss – metabolic adaptation – is a very real impediment. This adaptation varies from person to person and it can increase the time it takes to reach a person’s goal.

This is a topic for hot debate. So it’s one that many people use to rationalize strong beliefs about obesity, health, and weight. To some, this is one of many factors that explain obesity. It is an element that helps explain the physiology of obesity.

To others, it’s proof that any thought of obesity as a disease is pointless. It distracts from real problems like diabetes and heart disease. Because, they say, attempts to lose weight will wreck a person’s metabolism. So losing weight leads to worse, not better, health. This is a prominent narrative in debates about so-called diet culture.

A Factor, but Not a Barrier

The women in this study lost a remarkable amount of weight, primarily through a low-calorie (800/day) diet. Their metabolic adaptation varied greatly. For some, their metabolism was slower by more than 200 calories daily after weight loss. For others, it increased by more than 200. The average was a drop of 46 calories burned at rest per day.

But this variation did not create insurmountable barriers to reaching a weight loss goal. It was a factor that made it harder, even in this intensive program of only 800 calories per day. So in the real world, this is why some people find diets to have limited value. Other people find that they work just fine. The difference lies in physiology, not adherence, as Martins explains:

“Healthcare providers involved in obesity management, obesity researchers, individuals with obesity and the general public should pay close attention to these new findings. Delay in achieving weight loss goals, or achieving a weight loss lower than expected, is generally seen as the direct and sole result of reduced adherence to the intervention.”

This is why dealing effectively with obesity requires more than just diet and exercise. The physiology of obesity is very different from person to person – the illustration on the right from yet another paper makes this plain to see. Different people will need different kinds of help to overcome it.

The real barrier is that, all too often, people cannot gain access to anything beyond dietary approaches to obesity care.

Click here for the new paper in Obesity and here for a commentary that goes with it. For earlier research by Martins on this subject, along with commentaries, click here, here, here, and here.

Circulation Slowed, painting by Wassily Kandinsky / WikiArt

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January 28, 2022