How the Brain Responds to Bariatric Surgery

Most people – even many healthcare professionals – simply don’t get it. Because the popular concept of bariatric surgery is that it prevents people from eating – just by altering your gut. But the reality is that it works very differently. Bariatric surgery changes the signaling between the brain and the gut in ways that alters the physiological desire to eat. A new study in Diabetes Care brings this into focus.

fMRI Analysis of Brain Activation: Diet vs. Surgery

Victoria Salem and colleagues did a careful study of 35 subjects. All were receiving treatment for obesity. One group of 16 subjects were already set to receive a gastric bypass when they entered the study. The comparison group of 19 received a very low calorie diet for four weeks. Of course, subjects in the surgery group lost more weight after four weeks. After a year, they had lost yet more weight while subjects in the diet group had regained all the weight they initially lost.

But the real insights from this study come from changes and differences in brain function. In the diet group, losing weight led to subjects responding more to food cues in the reward centers of their brains. For surgery patients, the response was just the opposite. Responsiveness to food cues went down.

Also, subjects in the diet group used more brain function related to cognitive control in response to food cues after they lost weight. But weight loss through surgery had no effect on this. The surgery patients weren’t using any more conscious effort to control responses to food after surgery than before.

Finally, these researchers found indications that surgery engaged more appetite regulation in the hypothalamus than did the diet intervention.

A Grain of Salt

These authors don’t really talk about the limitations of their methods. But it’s worth pointing out that this is not a randomized, controlled study. The diet group is loosely – but not precisely – matched to the surgery group. So the differences we’re seeing here might or might not be entirely because of the interventions. It’s possible that differences between these groups at baseline could explain some of the differences in response to treatment.

Nonetheless, this study does provide insight to help explain how changes in the brain might influence the effects of bariatric surgery. Because right now, bariatric surgery is the most effective option for obesity treatment – with the longest lasting benefits.

Neuroscience can help us understand why.

Click here for the study, here and here for further reporting on it. For a good review of the interaction between bariatric surgery and the brain, click here.

fMRI Brain Image, created by Richard Watts / NIH Image Gallery on flickr

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July 10, 2021