Memory improves in older, overweight women after they lose weight by dieting, and their brain activity actually changes in the regions of the brain that are important for memory tasks, researchers said.
“Our findings suggest that obesity-associated impairments in memory function are reversible, adding incentive for weight loss,” said lead author Andreas Pettersson, from the Umea University, Sweden.
A special type of brain imaging called functional magnetic resonance imaging (functional MRI) allowed Pettersson and co-workers to see brain activity while the subjects performed a memory test.
The researchers randomly assigned 20 overweight, postmenopausal women (average age, 61) to one of two healthy weight loss diets for six months.
Nine women used the Paleolithic diet, also called the Caveman diet, which was composed of 30 per cent protein, 30 per cent carbohydrates and 40 per cent unsaturated fats.
The other 11 women followed the Nordic Nutrition Recommendations of a diet containing 15 per cent protein, 55 per cent carbs and 30 per cent fats.
Before and after the diet, the investigators measured the women’s body mass index (BMI) and body fat composition. They also tested the subjects’ episodic memory by instructing them to memorise unknown pairs of faces and names presented on a screen during functional MRI.
The name for this process of creating new memory is “encoding.” Later, the women again saw the facial images along with three letters. Their memory retrieval task, during functional MRI, was to indicate the correct letter that corresponded to the first letter of the name linked to the face.
The group’s average BMI decreased from 32.1 before the diet to 29.2 (below the cut-off for obesity) after six months of dieting, and their average weight dropped from 85 to 77.1 kg, researchers said.
Memory performance improved after weight loss, and Pettersson said the brain-activity pattern during memory testing reflected this improvement.
After weight loss, brain activity reportedly increased during memory encoding in the brain regions that are important for identification and matching of faces.
“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 results were presented at The Endocrine Society’s meeting in San Francisco.
