Weight-loss surgery can make you thinner. But can it make you smarter too?

It’s a question scientists have wondered about because they know the reverse is true. Studies have shown brain function declines in people who have too many extra pounds. Other research has shown that compared with people who are lean, those who are overweight are 26 percent more likely to develop some type of dementia and those who are obese are 64 percent more likely to meet that fate.

So a group of researchers from the University of Sao Paulo in Brazil conducted what they believe is the first study to track brain function in patients before and after they had weight-loss surgery. Their results suggest the brain does indeed benefit from bariatric surgery, though the effects measured were modest.

The researchers recruited 17 severely obese women who planned to have Roux-en-Y gastric bypass.

The average body mass index for the 17 women was 50.1. Six months after their surgeries, their average BMI had dropped to 37.2 — still high enough to qualify as severely obese, according to the Centers for Disease Control and Prevention.

Before they went under the knife, the women took an IQ test and six additional tests to assess their memory and executive function. They repeated all of the tests six months after surgery.

Compared with their initial results, the obese women improved on one of the tests — the Trail Making Test — after their surgeries, the researchers found.