The activity in a cortical area involved in self-regulation was the best correlate of weight loss in a study published today (October 18) in Cell Metabolism.
Previously, scientists thought that challenges to losing weight stemmed from imbalances between the hormones leptin, which produces a feeling of satiety, and ghrelin, which stimulates hunger. When people go on a diet, ghrelin levels go up and leptin levels go down.
To see how brain activity fits into dieting physiology, Alain Dagher, a neurologist at McGill University, worked with 24 overweight and obese people who were starting a 1,200-calories-per-day diet at a weight-loss clinic. Before starting the regimen, participants had fMRIs—imaging scans that show brain activity—while looking at pictures of either appetizing, sometimes high-calorie food, or of scenery. The researchers repeated the scans one month and three months into the diet.
Typically, food pictures activate the ventral medial prefrontal cortex, linked to desire, motivation, and value, Dagher says in a press release. Further, this region stimulates hunger when the body is burning more calories than it’s taking in, Dagher tells HealthDay.
Over the course of the study, the ventral medial prefrontal cortex responded less and less to the pictures of food, but the decline in activity was greatest in people who lost the most weight, Dagher says in the release. On the other hand, activity in the lateral prefrontal cortex, involved in self-regulation, increased over the course of the diet, and the more it was active, the more weight people lost.
“It’s a struggle, and we’re doing brain imaging of that struggle, the struggle between the desire to lose weight and the desire to eat tasty food,” Dagher tells HealthDay.
Although ghrelin levels did indeed go up, and leptin levels sunk, among the dieters, the changes in the levels of these two hormones did not prevent participants from losing weight and were less correlated with weight loss than activity in the lateral prefrontal cortex.
“These results suggest that weight loss treatments that increase self-control, such as cognitive behavioral therapy, may be helpful, particularly when stress is involved in leading to overeating,” Dagher says in the release.