Study: Teen Brains Change After Bariatric Surgery

— Reward, executive functioning improved with weight loss

Last Updated November 02, 2017

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NATIONAL HARBOR, Maryland -- Bariatric surgery may induce brain changes in obese adolescences, a new study found.

After undergoing vertical sleeve gastrectomy, adolescents with obesity showed improved executive skills and reward functioning, according to lead author Alaina L. Pearce, PhD candidate at Georgetown University in Washington, D.C., and colleagues.

The surgery group showed a larger gain in executive function since pre-surgery, measured using an N-Back test in an fMRI, compared to healthy controls. In the left prefrontal cortex -- specifically the left anterior insula and inferior frontal gyrus -- group X time interaction had a greater load-related activation (2-back > 1-back) reduction after surgery (P<0.05 corrected, k=242), thus reflecting activation patterns similar to healthy controls.

"We figured we would see some changes in adolescents after surgery since they are found in adults after surgery and because we knew our kids did better in school, but we really didn't know what type of changes or the amount of change we would see," Pearce and her research team explained to MedPage Today. "We found that the surgery group lost weight, improved cognition, and brain activation decreased after surgery, suggesting that brain functioning became more efficient."

During a monetary incentive delay task, the surgery group reported a significant improvement in reaction time compared to pre-surgery, dropping by a mean of 19.9 milliseconds (95 % CI 5.2-34.6; Cohen's d=1.42; P=0.018).

Findings from the pilot study were presented at the annual ObesityWeek meeting and simultaneously published in the journal, Obesity.

"We did the study for two main reasons," they noted. "The first is that we noticed that our patients after surgery seemed to do better in school and work and we wanted to understand why.

"The second is that we knew there were adult studies that found that weight loss improves brain function, but no one had ever studied that in kids. So we needed to see if the improvements seen in adults were the same in adolescents."

The study included 36 adolescents, ranging from 14 to 21 years of age. Among the cohort, 10 individuals were scheduled for vertical sleeve gastrectomy at study enrollment, with a mean BMI of 47.2. Additionally, there were 14 participants also with obesity (mean BMI 45.3), who were on a waiting list for the vertical sleeve gastrectomy because of either personal choice or due to a delay in insurance. A control group consisted of 12 healthy weight individuals. Exclusion criteria included an IQ of 74 or higher, no history of type 2 diabetes, psychiatric condition, or neurological disorder, nor use of any psychotropic medications.

Participants underwent a series of cognitive tests assessing executive, reward, and episodic memory assessments performed in an fMRI at two separate testing sessions, 4 months apart. Participants who underwent surgery had initial cognitive testing 1 to 4 weeks prior to surgery, and then 3 to 4 months post-surgery.

Only 6 surgery and 9 wait list participants underwent cognitive testing because only those with a BMI under 50 could fit in the MRI bore.

Surgery participants lost an average of 9.06 BMI units after gastrectomy, while those on the wait list gained 1.27 BMI units during the study period.

"Perhaps, most surprising was that the wait-listed control kids, who gained weight in the 3-month interval, increased brain activation, suggesting that brain functioning became less efficient with weight gain," Pearce and her group highlighted.

There were no significant differences seen in the surgery and wait list groups for episodic memory.

In regards to future studies, they told MedPage Today, "We are currently planning to replicate our results with a larger sample and also we want to want to see if these improvements in brain functioning relate to improved behaviors such as eating less and exercising more and whether kids improve in their school performance."

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The study was funded by a grant from the National Institute of Diabetes and Digestive and Kidney Diseases. The authors declared no conflicts of interest.