Weight Loss Improves Memory for Older, Overweight Women

Weight loss in postmenopausal, overweight women leads to improved memory. In a recent study, women who dieted to lose weight experienced changes in the areas of the brain that handle memory function, providing one more compelling reason to aim for a healthy weight.

Prior studies showed that episodic memory – remembering things that happen over the course of a lifetime – was impaired in obese people.

"Our findings suggest that obesity -associated impairments in memory function are reversible,” says the study’s lead author, Andreas Pettersson, MD.

The researchers set out to learn if memory could be improved with weight loss and how better memory compared with differences in brain activity. The study involved 20 postmenopausal females at an average age of 61. Eleven women were assigned to follow the Nordic Nutrition Recommendations of diet – 55 percent carbohydrates, 30 percent fats, and 15 percent protein. The other nine women went on the Paleolithic diet (Caveman diet ) – 30 percent carbohydrates, 30 percent protein, and 40 percent unsaturated fats. The diets lasted for six months.

Body mass index and body fat composition were measured prior to the diets, and again after.

The research team used functional magnetic resonance imaging (MRI) to analyze brain activity during memory tests. Episodic memory was tested using pairs of previously unknown faces and names, which appeared on a screen. The volunteers were asked to memorize the new information, a process called “encoding.” At a later time, the subjects were asked to match the faces to the names.

Data from the two groups was combined, since there were no differences in the functional MRI data or body measurements. Data revealed the group’s averages as a pre-diet BMI of 32.1 and post-diet BMI of 29.2, which is no longer in the obese category; and pre-diet weight of 85 kilograms (188.9 pounds) and post-diet weight of 77.1 kilograms (171.3 pounds).

In tests following the weight loss , the researchers found that brain activity was increased in parts of the brain that are used for identifying and matching faces, and the subjects showed improved memory. It was also noted that there was a decrease in brain activity in those parts of the brain involved with retrieving episodic memories. That points to more efficient retrieval, according to Pettersson.

"The altered brain activity after weight loss suggests that the brain becomes more active while storing new memories and therefore needs fewer brain resources to recollect stored information," he said.

The research was presented at the 95th Annual Meeting of The Endocrine Society. Pettersson is a PhD student at Umea University, Umea, Sweden. Funding was provided by the Swedish Research Council and the Swedish Heart-Lung Foundation.