We’ve all heard of *anorexia nervosa, *the disorder characterized by a distorted self-image of being “too fat,” in spite of the opposite being true.
I’m wondering whether there are people with the opposite disorder, i.e. a self-image of being “too thin,” in spite of being obese. AFAIK, most overweight people know that they’re overweight; their self-perception is realistic (within certain parameters). But aren’t there people who constantly feed themselves in order to overcome their perceived thinness? And what would this disorder be called?
The opposite of anorexia is probably best called hyperphagia.
Hyperphagia, AFAIK, is never due to a deranged impression of self as being too thin. Rather, it can result from endocrine disorders such as hyperthyroidism and uncontrolled diabetes, be part of an eating disorder syndrome (such as anorexia-bulimia), and, most interestingly, be due to problems affecting the hypothalamus.
The hypothalamus is that part of the brain responsible for very basic things such as heat regulation, appetite, and thirst. It also is the brain’s final control mechanism for the secretion of many hormones.
With disease or injury to the hypothalamus, a previously normal weight, normal-eating person can become a ravenous glutton. They may eat, literally, non-stop and spend much of their time searching for and hording food. Sometimes, people can have congenital abnormalities involving the hypothalamus, e.g. Prader-Willi Syndrome. It also appears that purely biochemical/hormonal problems can affect the hypothalamus in much the same way.
Some bodybuilders suffer from the delusion that they’re small, fat, and weak no matter how big they actually are. It’s generally referred to as bigorexia nervosa.
There is also Muscle dysmorphia. People suffering from this may not be overweight, and in fact train or even compete in bodybuilding events. But, like anorexics, they do not have a good estimation of their own body mass. This can lead to extreme and sometimes unhealthy behaviors to “correct” their bodies to what they feel they should look like.
See also Muscle Dysmorphia in Male Weightlifters: A Case-Control Study.