Habit Could Explain Poor Eating Decisions Made By Anorexics

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We’ve learned a lot about human behavior over the years, but one thing that continues to baffle scientists and psychologists alike is why, as intelligent beings, we repeatedly make bad choices, despite knowing full well the potential consequences of our actions. People with anorexia are just one example of this, but we may finally be getting somewhere with unraveling the underlying neural mechanisms of this incredibly complex eating disorder.

According to new research, when deciding what to eat, anorexics display heightened brain activity in an area known to play a role in habitual behavior. That’s interesting, because for a long time it has been assumed that the persistent maladaptive food choices in those with the disorder are the result of some unexplained ability to override or displace one of the most fundamental drives of living organisms: the need to eat and stay nourished.  

This idea doesn’t quite fit the bill, though, because even when those with anorexia nervosa choose to undergo treatment and commit to change, they still make poor decisions with regards to food. More specifically, when given the choice, even those in recovery show a propensity to go for low-calorie, low-fat foods, in spite of their goal to gain weight and knowledge that, ultimately, this choice could lead to poor health, starvation and even death. Scientists therefore saw this intriguing pattern of behavior as a possible window to understand more broadly the mechanisms behind persistent maladaptive behavior in humans.

For the investigation, published in Nature Neuroscience, scientists in the U.S. used a technique called functional magnetic resonance imaging (fMRI) to scan the brains of 21 women diagnosed with anorexia nervosa and 21 healthy controls as they took part in a decision-making task. Participants were asked to make a series of choices between food items that ranged in both taste and health. To make sure there was meaning behind the choices, participants were randomly given one of the items they selected as a snack after the task.

As anticipated, they found that those with anorexia were significantly less likely to choose the higher-fat foods when compared with controls. And when brain activity was examined, the team found that during this decision-making task, the anorexia patients showed increased activity in the dorsal striatum, a region linked with habitual control of actions.

Food choices were then assessed in a different, more true-to-life situation the following day, whereby participants were offered a buffet lunch meal. Sure enough, both brain activity in the dorsal striatum and frequency of high-fat food choice in the previous task correlated with the number of calories they consumed during the buffet.

Taken together, the findings indicate that when making decisions regarding food, those with anorexia engage their dorsal striatum to a greater extent than those without the condition, suggesting a previously underappreciated role of habit based on past behaviors. But this study has implications further than anorexia: the dorsal striatum has also been linked with disorders like gambling and substance abuse, so it may give us a broader perspective on maladaptive behaviors in general.

“There is tremendous value in studying how the brain makes decisions in both health and disease,” study coauthor Daphna Shohamy said in a statement. “Understanding how common brain circuits for decision-making contribute to seemingly unrelated disorders will allow researchers to focus on core disturbances and leverage treatment advances across different disorders.”

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