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How neuroscience explains eating disorders

Food is a basic necessity of life - we literally can’t live without it. But our relationship with food can be...complicated. So the existence of eating disorders isn't really that surprising. we’re going to get a little bit heavy.

How neuroscience explains eating disorders

Eating disorders are a difficult and serious topic, but this week we’re going to talk about some advances scientists have made in understanding these disorders in order to develop better, more effective treatments The term “eating disorder” actually covers a broad range of conditions. The two most commonly depicted in popular media are anorexia nervosa and bulimia.
Anorexia nervosa is characterized by extreme caloric restriction - people who suffer from anorexia usually maintain strict control over what they eat, eating only a few hundred calories per day, if they eat anything at all. Because of this, people with anorexia frequently show extreme weight loss Bulimia usually entails cycles of binging and purging - eating a lot of food, then making themselves vomit, using laxatives, or exercising excessively to purge their bodies of the calories they’ve just consumed. Bulimia can be harder to see, because often people with bulimia maintain a fairly steady weight. These disorders affect mostly young women, but they are becoming more common in men, too These aren’t the only two eating disorders out there - there’s also binge-eating disorder, where an individual loses control over their eating and consumes far more calories than recommended in a short period of time. This can lead to obesity and other related health problems, and it doesn’t discriminate - both men and women experience binge eating disorder at about the same rate.

Eating disorders are no small problem, either. About 30 million people in the United States suffer from an eating disorder. That would be like all of Boston, Houston, Chicago, Phoenix, and San Francisco combined! Many people may have the misconception that eating disorders aren’t really disorders at all - that they’re really just a reflection of the vanity or greediness of an individual. In reality, eating disorders are serious psychiatric illnesses, recognized by doctors and psychologists. And it turns out that there’s some pretty interesting neuroscience going on, too. One of the things that makes eating disorders so serious is that they’re very hard to treat; up to a third of people who receive treatment for anorexia end up relapsing. And many of those who recover physically still struggle with obsessions about their weight and food intake.
A study in published in summer of 2015 found that part of why recovery is so difficult may be that anorexia and other eating disorders aren’t a case of strong willpower or picky eating. In fact, anorexic behaviors seem to become habits - so deeply ingrained that sufferers aren’t even aware of their food choices. This particular study used functional magnetic resonance imaging, or fMRI, which uses blood flow in the brain to help scientists track brain activity changes. 21 patients being treated for anorexia nervosa, along with 21 control participants, were asked to rate food on a scale from 1 to 5, where 1 was “unhealthy”, 3 was “neutral”, and 5 was “healthy”. They were also asked to rate food on a taste scale from 1 to 5 - 1 was “bad”, 3 was “neutral”, and 5 was “good”.
A food item they had ranked as “neutral” on both taste and heathiness was randomly selected, and while participants were having their brains scanned in the fMRI, they were asked to make different food choices between the “neutral” item and other foods they had previously ranked. What the scientists found was that individuals with anorexia had a lot more activity than controls in a brain region called the dorsal striatum when they were making decisions about which food to eat. The dorsal striatum is a region that’s associated with reinforcement learning - basically habit formation - and decision making. These results indicated to the scientists that it wasn’t so much that the women with anorexia were choosing not to eat, or choosing to only eat super-healthy food - but rather that they were unconsciously slipping back into a deeply ingrained habit. So it might be that treating eating disorders successfully requires more of a habit-breaking approach, like we use with substance abuse, rather than simply telling sufferers to “stop acting that way”.
There’s also evidence that other brain regions show different patterns of activity in patients recovering from anorexia in a brain region called the insula. The insula is a part of the cortex that helps the brain identify what it’s tasting. Along with other brain regions, like the amygdala and the orbitofrontal cortex, the insula helps us identify what tastes we like and don’t like. More activity is seen in these regions when we’re hungry, and less when we’re full. These brain areas, along with the ventral striatum, help determine how motivated we are by food. When individuals with normal eating patterns are given a sweet-tasting stimulus during brain imaging, there is a lot of activity seen in their insula. The more they report liking sugar, the more activity in the insula.
On the other hand, patients who are recovering from anorexia show lower levels of activity in the insula - which might indicate that they find the sugary taste less pleasurable than their control counterparts. These individuals appear to actually experience taste differently, even after recovery! Scientists interpret this as indicating that people who suffer from anorexia are less driven by hunger and appetite signals than usual. And with less motivation to eat, it may be easier for these individuals to drive themselves to the edge of starvation. Researchers are still working to understand the neuroscience of eating disorders, and are currently limited by available scientific techniques to help them break down the biology of the brain. But these results are helping doctors and psychologists determine their approach to treatment. For example, since anorexia seems to be connected to ingrained habits, doctors now recommend that patients in recovery try eating in new places, to help break the habits formed by disordered eating. And hopefully as scientists continue to develop new techniques, we can continue to develop new treatments. In the mean time, there are a lot of resources out there to help individuals with disordered eating recover.