More Than Weight Loss: Bariatric Surgery and Diabetes

A new study revives an old question. Isn’t the benefit of bariatric surgery for people with diabetes more than just weight loss? In the December issue of Diabetes Care, Blandine Laferrère and colleagues write:

“Our data show the time course of changes in β-cell function after RYGB. The improvement in β-cell function after RYGB, but not changes in weight loss or insulin sensitivity, drives diabetes remission.”

In other words, if we want to put diabetes into remission with a gastric bypass, weight loss does not matter so much as β-cells and how well they’re functioning.

A Small and Careful Study

This is a two-year study of just 29 subjects with severe obesity and diabetes who had gastric bypass surgery. The researchers measured β-cell function after a glucose infusion at baseline, 3, 12, and 24 months. They also tracked body weight, fat mass, waist circumference, and insulin resistance. All of these measures improved significantly after surgery. Five persons achieved a full remission of their diabetes. For the rest of the subjects, 16 had a partial remission and eight had no remission.

The goal was to understand what factors might be critical for in predicting who would have a remission. The results showed that neither weight loss nor insulin sensitivity was important for this. Only β-cell function was. The improvement was only apparent after 12 months and it was only significant in the subjects who achieved a full remission.

Commenting on this finding, obesity medicine physician Fatima Cody Stanford tells us:

“In caring for people living with obesity, it is plain to me that the benefits of metabolic and bariatric surgery extend well beyond weight loss alone. This study provides another piece of the puzzle for understanding the bigger picture.”

More to Learn

Clearly, this is just one small, but careful study. We need to know much more. For one thing, this study only provides insight about bypass surgeries. David Arterburn tells us that for bypass surgeries, these present findings are not surprising:

“We always knew that there was a weight-loss independent effect of RYGB happening because so many patients were leaving the hospital with no need for diabetes medications right after bariatric surgery.”

But the metabolic effects of gastric sleeve surgery can be different. Since gastric sleeves are now the most common procedures for bariatric surgery, this study cannot tell us the whole story. The mechanisms that drive remissions after a gastric sleeve may be different than they are with a bypass.

But Weight Loss Is Not Irrelevant

And finally, we should bear in mind that weight loss is not altogether irrelevant for improvements in diabetes. In fact, with data from both bypass and sleeve procedures, Arterburn and colleagues found that weight loss was indeed an important predictor of diabetes remission – up to a threshold of 20 percent weight loss. Beyond that, further reductions in weight didn’t make a difference.

We would do well to remember that many factors are at work when someone is dealing with obesity. Simple answers might be attractive, but they can easily mislead us.

Click here for the Laferrère study and here for Arterburn’s earlier study.

Cross Section of a Human Pancreas, photomicrograph from the Berkshire Community College Bioscience Image Library, released to the public domain, CC0 1.0

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December 10, 2021