PET Imaging Reveals Brain Benefits from Weight Loss After Bariatric Surgery

Imaging studies revealed that weight loss surgery has been found to suppress changes in brain metabolism associated with obesity and improve cognitive function involved in planning, strategizing, and organizing. Therefore, researchers have hypothesized that a specific surgical procedure could reduce risk of Alzheimer’s in obese people.

The findings were published online August 26, 2014, in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism (JCEM). Obesity can overload the brain as well as other organs and obese individuals face a 35% higher risk of developing Alzheimer’s disease compared to normal weight people. Bariatric surgery is used for individuals who are severely obese lose weight by restricting the amount of food they can eat before feeling satiated by reducing the stomach’s size or limit the absorption of nutrients by removing part of the small intestine from the path food takes through the digestive tract. Some procedures, such as Roux-en-Y gastric bypass (RYBG) surgery, use a combination of these techniques. This study was the first to assess brain activity in women before and after bariatric surgery.

“When we studied obese women prior to bariatric surgery, we found some areas of their brains metabolized sugars at a higher rate than normal weight women,” said one of the study’s authors, Cintia Cercato, MD, PhD, from the University of Sao Paolo (Brazil). “In particular, obesity led to altered activity in a part of the brain linked to the development of Alzheimer’s disease—the posterior cingulate gyrus. Since bariatric surgery reversed this activity, we suspect the procedure may contribute to a reduced risk of Alzheimer’s disease and other forms of dementia.”

The longitudinal study examined the effect of RYBG surgery on the brain function of 17 obese women. Researchers used positron emission tomography (PET) imaging scans and neuropsychologic tests to evaluate brain function and activity in the participants prior to surgery and six months after the procedure. The same tests also were run once on a control group of 16 lean women.

The obese women, before undergoing surgery, had higher rates of metabolism in specific regions of the brain, including the posterior cingulate gyrus. Following surgery, there was no evidence of this exacerbated brain activity. Their brain metabolism rates were comparable to the activity seen in normal weight women. After surgery, the obese women also performed better on a test gauging executive function than they did before the procedures. Executive function is used in planning, organizing, and strategizing. Five other neuropsychologic tests measuring various aspects of memory and cognitive function demonstrated no change following the surgery.

“Our findings suggest the brain is another organ that benefits from weight loss induced by surgery,” Dr. Cercato concluded. “The increased brain activity the obese women exhibited before undergoing surgery did not result in improved cognitive performance, which suggests obesity may force the brain to work harder to achieve the same level of cognition.”

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University of Sao Paolo