Bulimia nervosa is an eating disorder marked by bouts of out-of-control binge-eating followed by self-induced vomiting or use of laxatives or diuretics to purge. People with bulimia may use other compensatory behaviors after bingeing, such as fasting or overexercising. There is no way to tell by looks alone whether a person is bulimic, and both bingeing and purging are done secretly. People with bulimia often have coexisting psychological illnesses, such as depression, anxiety, or substance use disorder. Purging may lead to any of a number of physical dysfunctions, including electrolyte imbalances, gastrointestinal troubles, and dental problems. An estimated one to four percent of females have bulimia nervosa during their lifetime. The prevalence in males is unknown, but bulimia nervosa is far less common in males than females. The disorder most commonly begins in the late adolescence and early 20s, but can go undetected until the 30s or 40s.