Food and Behaviour Research

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23 March 2015 - ScienceDaily - Hunger versus reward: How do anorexics control their appetite?

Many adults, regardless of their weight, resolve to avoid fatty foods and unhealthy desserts. But despite one's best intentions, when the moment for decision comes, that chocolate lava cake is often too enticing and self-control vanishes.

This behavior is normal because hunger increases the intensity of food rewards. Yet, individuals with anorexia nervosa (AN), despite their state of starvation, are able to ignore such food-related rewards.

A new study by Dr. Christina Wierenga, Dr. Walter Kaye, and colleagues, published in the current issue of Biological Psychiatry, sheds new light on the brain mechanisms that may contribute to the disturbed eating patterns of anorexia.

They examined reward responding in relation to metabolic state (hungry or satiated) in 23 women recovered from AN and 17 healthy women without eating disorder histories (e.g., the comparison group). Women with active AN weren't studied to reduce potential confounds related to starvation.

The healthy women, when in a state of hunger, showed increased activity in the part of the brain that motivates the seeking of reward, but the women recovered from AN did not. The recovered women also exhibited increased activation of cognitive control circuitry regardless of metabolic state.

Thus, this study found that women who have recovered from anorexia nervosa show two related patterns of changes in brain circuit function that may contribute to their capacity to sustain their avoidance of food.

First, hunger does not increase the engagement of reward and motivation circuits in the brain. This may protect people with anorexia from hunger-related urges. Second, they showed increased activation of executive 'self-control' circuits in the brain, perhaps making them more effective in resisting temptations.

"This study supports the idea that anorexia nervosa is a neurobiologically-based disorder. We've long been puzzled by the fact that individuals with AN can restrict food even when starved. Hunger is a motivating drive and makes rewards more enticing," said Wierenga.