Weight-loss surgery can make you thinner. But can it make you smarter too?
The researchers recruited 17 severely obese women who planned to have Roux-en-Y gastric bypass, a procedure that shrinks the stomach to the size of an egg and diverts food past a good portion of the small intestine. Both measures reduce the amount of nutrients and calories the body can absorb from food.
Another group of 16 women served as controls. Their ages and educational levels were essentially the same as for the obese women, but their BMIs were much lower (22.3, on average). The lean women took all the same tests as the obese women, though they did so only once.
It turned out that women in both groups did equally well on the cognitive tests. But compared with their initial results, the obese women improved on one of the tests – the Trail Making Test – after their surgeries, the researchers found.
The differences in brain scans were more pronounced. Before the surgeries, the obese women's brains appeared to be working harder than the brains of the lean women. That was especially true in areas of the right hemisphere that become active when people have to compensate for cognitive decline, the researchers wrote. However, after the surgeries, these differences "were no longer noticed," they added.
Overall, the researchers concluded that being obese increases one's risk of Alzheimer's by an amount similar to the effect of having the e4 version of the APOE gene. Although it's impossible to change your APOE gene, the good news for those who are obese is that they can probably reduce their risk of cognitive decline by losing weight, the researchers wrote.
The study was published Tuesday in the Journal of Clinical Endocrinology and Metabolism.