People suffering from bulimia nervosa are caught up in a cycle of overeating/bingeing and then purging to prevent any gain in weight.  They feel out of control of their eating, and their purging behaviour adds to their sense of personal shame and distress.  Some use compensating behaviours in addition to or instead of purging, e.g. over-exercising or restricting food. 

Purging is typically achieved by self-induced vomiting or taking laxatives or diuretics.  This behaviour seems like the answer to a problem - how to eat and not gain weight, but it mainly causes fluid loss in fact, rather than calorie loss, and it damages the body.  

Sufferers of bulimia have an intense fear of becoming overweight, and usually keep within the normal body weight ranges, though their weight may fluctuate.  This means that bulimia can be kept hidden, unlike anorexia. 

Bulimia can develop out of anorexia, and some sufferers do follow a cycle of strict dieting and then a binge-purge. 

The diagnostic criteria used by the NHS:

Symptoms include:

Damaging consequences of vomiting include:

Damaging consequences of laxative misuse include:

Over time, laxative use increases to high doses as tolerance to the laxative develops.

Some observable signs: