The treatments actually are somewhat similar.
I'll start with bulimia nervosa, which is easier to treat than anorexia nervosa.
The binge eating of bulimia nervosa is not food addiction. It's actually a response to starvation in the same way that if you held your breath for a minute or two you would gasp for air because you were starved for oxygen. A certain percentage of the population, about 5%, will respond to hunger with these episodes of binge eating. That makes them different from everybody else.
To treat bulimia you have to feed people. In our day hospital we feed them lunch, afternoon snack, and dinner, and teach them strategies to resist urges to binge and to purge, because these things get tangled up into stressors and stuff like that. The fundamental treatment is to feed people. You eat your way out of bulimia, oddly enough. People in our day hospital service will stop bingeing in a week or two if they are able to do what we ask them to do.
The treatment for anorexia nervosa is similar in some ways. Although most people with bulimia don't like binge eating, and they'll do whatever they need to do to get rid of it, for anorexia nervosa, the decisional balance is often much more finely balanced, because the illness has advantages to the person as well as disadvantages. The fundamental thing you have to do is help people to eat and gain weight. That's the behavioural change that has to occur first.
Then people have to address the underlying cognitive set, the way people think about weight, shape, food, and eating, which has to happen with bulimia as well. Then people have to deal with their other psychological problems that underlie or are associated with the illness. Depending on what those are, that could be the work of many years.
About 60% of my patients have chronic complex post-traumatic stress disorder. They've been sexually or physically abused. They will work for eight or ten years to recover from that, although we have some novel treatments for PTSD that we're working on right now that are looking to be very promising.