Let’s take a brief look at the study at the origin of these articles. Participants were 109 bariatric surgery patients and 41 obese people (controls) who had not undergone surgery. Bariatric surgery refers mostly to gastric bypass surgery, which creates a smaller stomach and bypasses part of the small intestine. The bariatric patients were enrolled in the Longitudinal Assessment of Bariatric Surgery project conducted, among others, by researchers at Kent State university and Columbia University.
The memory of the 150 participants was assessed before the surgery as well as 12 weeks after. Results showed that the memory of the surgery patients had improved whereas the memory of the obese controls had declined.
Comments: Obesity is among the risk factors for Alzheimer’s disease. It is also becoming apparent that being obese tend to be linked to memory problems in general. So it seems to make sense that losing weight should reverse this tendency. However the mechanisms by which this may happen are largely unknown: What causes the memory problems to start with is a mystery. Given that both a balanced diet and regular physical exercise are key to brain health, there are probably more than one variable at work here.
In sum, more research is need to understand what links obesity to memory problems. It is not known either whether losing weight without undergoing surgery would have similar positive effects on memory.