In the past it was believed that people with bulimia nervosa had a binge-eating disorder and that they dieted in order to counteract the effects of a binge. Although it is true that people sometimes restrict their eating after binging, we now know that dieting in fact precedes, and is the major cause of binge-eating.
Dieting causes binge-eating primarily because it results in a state of deprivation in the body. The body can only tolerate being deprived of essential nutrients for so long and then it rebels and overeats to compensate for what it hasn’t been getting. In the same way that people who become extremely thirsty tend to drink more than usual, people who’s bodies are extremely hungry, will tend to binge. How long it takes to develop binge-eating varies. Some people manage to maintain extreme restriction for a long time without bingeing, however for the vast majority of people, and for 50% of people with anorexia, restriction will at some point result in binge-eating. This is often taken as a sign of failure or weakness, however it is actually near impossible to override a physiological urge to binge
The body makes significant adaptations in response to both restriction and bingeing, meaning that the effect of bingeing on the body can change over time. Firstly, if the body learns that it has to exist on a small amount of energy (as it does in those who chronically diet), it slows its metabolic rate down in order to use food more efficiently. Dieting actually reduces the metabolic rate by around 15-30% and reduces the amount of energy expended during activity. This compensation is found irrespective of the body size of the individual. The longer a person diets for the more the metabolic rate is slowed, and the longer it takes for the metabolic rate to recover.
This has important implications for understanding the effects of binge-eating cycles. It is likely that weight loss becomes increasingly difficult each time a person tries to restrict their food intake, and that the calories taken in during binges are less likely to be burned as fuel and are stored more readily by the body as fat. This is one of the reasons why people with bulimia nervosa tend to gain weight over time, even if their eating doesn’t seem to have changed. This weight gain (or increased difficulty in losing weight) makes it more likely that people will try and diet. However this only serves to increase the frequency and intensity of being eating. Thus a vicious cycle begins.
Vomiting and using laxatives often begin as ways of regaining control after “over-eating.” These practices soon result in even greater breakdown in control since they “legitimize” binging (“It’s all right to binge, because I can get rid of it all afterwards”). They may also contribute to a physical relief after the fullness of binging or eating, and the person may eventually feel she must vomit or use laxatives after every meal or at the end of every day to try to get back the sense of relief. Although the individual may initially lose weight through purging, this is most often temporary as the effectiveness of vomiting becomes limited over time (see blog post: the ineffectiveness of purging). Although vomiting “solves” the short-term problem of getting rid of unwanted food that may lead to weight gain, in fact it only gets rise of around 30% of calories consumed during a binge, and actually makes it more likely that a person will binge as it increases hunger and urges to binge. Thus over time, people who purge after bingeing are also more likely to see an increase in bingeing and resulting weight gain.
Taking laxatives can also be part of this cycle. Regular laxative use can result in a physiological reliance on the laxatives. This may be because the bowel’s normal muscle contracting ability is impaired by repeated laxative use due to damage to intestinal nerves. Severe constipation or water retention can result when laxatives are not used, so that it seems that continuing to take the laxatives is the only way to continue “regular” bowel movements. Besides being extremely dangerous, laxatives are a completely ineffective method of trying to prevent the absorption of calories. In fact all laxatives get rid of is water, thus removing essential hydration from the body.
Occasionally bingeing eating occurs solely because of these physiological effects, however in bulimia nervosa there can often be emotional triggers to bingeing as well. In these circumstances bingeing tends to be triggered by intense emotions or as a desire to escape from strong emotions. This means that when bingeing stops, strong emotions may start to reveal themselves. For these people, it can be very important to seek support from a professional to help them to identify, understand and cope with these strong emotions.