Bariatric Surgery Appears to Ease Brain's Response to Food, Study Finds

Surgery to help people lose weight may work by limiting not only how much they can eat, but also whether they want to eat, a new study has found.

A reduced desire to overeat may be linked to improved glycemic control that follows bariatric surgery, according to research in the new issue of Diabetes Care, the journal of the American Diabetes Association (ADA).

In the study, researchers measured activity in the brain’s reward centers in 2 groups of patients with type 2 diabetes (T2D): 12 people who had received the Roux en-Y gastric bypass procedure at least 6 months prior, and 12 who had not had surgery.

Using functional magnetic resonance Imagining (fMRI), the researchers found that those who had surgery had less activity in the brain’s reward centers when shown pictures of food than those without surgery. The results were confirmed in behavorial tests giving during the scans.¹

The study, led by Sabine Frank of the University of Tubingen in Germany, is consistent with recent results from the University of Texas Southwestern Medical Center; researchers there reported in the July issue of Obesity that brain scans showed severely obese women had very different responses to food than others—that their reward centers, in effect, kept telling them to eat even after they were no longer hungry.²

The findings come as more is understood about the complexity of obesity and its genetic and environmental causes. Professional societies are increasingly seeing value in bariatric surgery, both to help patients lose weight and to reverse diabetes, even in patients who have not reached a body mass index (BMI) that would classify them as obese.

In recent months, the American Association of Clinical Endocrinologists updated guidelines for obesity that called for covering more forms of treatment, and the ADA issued guidelines for when surgery should be used to treat diabetes, even in pediatric patients.

In the Diabetes Care study, patients were matched for age and current BMI, as well as their glycated hemoglobin (A1C) before surgery, as the surgical group had achieved significant improvements in A1C along with weight loss. Authors of this new study acknowledged limitations, including their inability to determine whether improved glycemic control could, by itself, cause the differences in brain activity.

Methods and Results. Participants arrived for the study after fasting.at least 3 hours. The completed questionnaires to gauge current hunger, mood, and eating traits.During the fMRI, patients were shown pictures of food—both high- and low-calorie—and asked to rate each photo, first for how much they wanted the food “now,” and second for how much they liked it.

Imaging evaluations were controlled for vascularization, as this would be affected by age, medication and diabetes status. Evaluations showed no differences in mood between the 2 groups.

Results showed the group without surgery had higher ratings for both wanting and liking tasks than the surgical group, and the nonsurgical group also rated higher on liking than wanting. The surgical group did better on tests of cognitive restraint.

As for the imaging results, the authors wrote, “Neuronal activation showed distinct differences between the groups and between the 2 task conditions,” They found that obese patients with T2D without surgery and with impaired glycemic control showed substantially higher activations in the brain areas associated with inhibition and reward, compared with those whose A1C had improved after surgery.

Notably, they wrote, because they had BMI matched samples, “the observed neuronal effects do not depend on BMI differences. Instead, the differences in food reward-association brain function might be based on substantial weight loss and improved glycemic control.”

References

1. Frank S, Heinze JM, Fritsche A, et al. Neuronal food reward activity in patients with type 2 diabetes with improved glycemic control after bariatric surgery. Diabetes Care. 2016; 39:1311-1317.

2. Puzziferri N, Zigman JM, Thomas BP, et al. Brain imaging demonstrates a reduced neural impact of eating in obesity. Obesity. 2016; 24(4):829.