What is it?
Bulimia nervosa is an eating disorder characterized by binge eating followed by purging. During the binge episode, the affected eats a large amount of food in a short time, and during the purge episode, they try to “get rid of it” by e.g. vomiting or using laxatives. Most people with bulimia are at normal weight.
Bulimia affects about 2-3% of women at some point in their lives. It is most common in young women in the developed world.
What causes it?
The risk of developing bulimia is much higher for people with relatives who have suffered from it: genetics is thought to be responsible for 30-80% of the overall risk. Other predisposing factors include psychological stress, living in a culture that idealizes one body type, poor self esteem, and obesity.
What happens during it?
The mechanisms of bulimia has most likely something to do with a part of our brain called hypothalamus. Among other things, it regulates our eating behavior. It has a satiety center, and its stimulation leads to a feeling of satiety and wellbeing. It also has a part called the lateral hypothalamus, and its stimulation leads to more eating. Together these parts keep our bodies at a set weight.
It has been found that certain neurotransmitters, such as serotonin, in these areas of the hypothalamus is linked to satiety. It has also been suggested that a reduced ability to respond to serotonin is a contributing factor of developing bulimia.
Our bodies usually know what chemicals they want. If you stop breathing for a while, your body senses from the amount of carbon dioxide in your blood that it probably also has too little oxygen, and it makes you breathe. The binge-eating of bulimia may be compared to a process like this. Foods high in sugar are turned into serotonin, and if your hypothalamus senses that it needs more of it, it has ways of getting what it wants. That might be why the bulimic’s urge to eat is so big: it’s not a normal case of trying to resist chocolate, it’s a war against their hypothalamus.
The serotonin approach to bulimia is also supported by the fact that it is accompanied by a distorted self image. People with the disease often feel “fat” even though they are at a normal weight. It is quite established that many cases of depression are linked to low serotonin levels and that these low levels lead to a sense of a lower status in society than is accurate. Eating disorders are often presented with depression, and it’s not that far-fetched to think that some of this sense of a lower status may cause the affected to think that they are “fat”, especially in a society where women’s value is measured (even if subconsciously) by their looks.
How can it be treated?
Many different kinds of therapy are used to treat bulimia. The perhaps most promising is cognitive behavioral therapy, which through several measures aims to challenge the automatic thought patterns of the affected. Frequent vomiting damages the teeth and the digestive tract, and sometimes these physical symptoms need to be taken care of. As mentioned, serotonin levels are thought to play a key role in bulimia, and there is some evidence for the effectiveness of using antidepressants that affect these neurotransmitters.
Sources: http://serendip.brynmawr.edu/bb/neuro/neuro98/202s98-paper3/Hirst3.html, http://www.ncbi.nlm.nih.gov/pubmed/16499999, https://en.wikipedia.org/wiki/Bulimia_nervosa