Claim: Anorexia nervosa rates in the developing world are unclear.

Anorexia nervosa , often referred to simply as anorexia , is an eating disorder characterized by a low weight , fear of gaining weight , a strong desire to be thin , and food restriction . Many people with anorexia see themselves as overweight even though they are in fact underweight . If asked they usually deny they have a problem with low weight . Often they weigh themselves frequently , eat only small amounts , and only eat certain foods . Some will exercise excessively , force themselves to vomit , or use laxatives to produce weight loss . Complications may include osteoporosis , infertility and heart damage , among others . Women will often stop having menstrual periods .   The cause is not known . There appear to be some genetic components with identical twins more often affected than non-identical twins . Cultural factors also appear to play a role with societies that value thinness having higher rates of disease . Additionally , it occurs more commonly among those involved in activities that value thinness such as high-level athletics , modelling , and dancing . Anorexia often begins following a major life-change or stress-inducing event . The diagnosis requires a significantly low weight . The severity of disease is based on body mass index -LRB- BMI -RRB- in adults with mild disease having a BMI of greater than 17 , moderate a BMI of 16 to 17 , severe a BMI of 15 to 16 , and extreme a BMI less than 15 . In children a BMI for age percentile of less than the 5th percentile is often used .   Treatment of anorexia involves restoring a healthy weight , treating the underlying psychological problems , and addressing behaviors that promote the problem . While medications do not help with weight gain , they may be used to help with associated anxiety or depression . A number of types of therapy may be useful including an approach where parents assume responsibility for feeding their child , known as Maudsley family therapy and cognitive behavioral therapy . Sometimes people require admission to hospital to restore weight . Evidence for benefit from nasogastric tube feeding , however , is unclear . Some people will just have a single episode and recover while others may have many episodes over years . Many complications improve or resolve with regaining of weight .   Globally , anorexia is estimated to affect 2.9 million people as of 2015 . It is estimated to occur in 0.9 % to 4.3 % of women and 0.2 % to 0.3 % of men in Western countries at some point in their life . About 0.4 % of young females are affected in a given year and it is estimated to occur ten times less commonly in males . Rates in most of the developing world are unclear . Often it begins during the teen years or young adulthood . While anorexia became more commonly diagnosed during the 20th century it is unclear if this was due to an increase in its frequency or simply better diagnosis . In 2013 it directly resulted in about 600 deaths globally , up from 400 deaths in 1990 . Eating disorders also increase a person 's risk of death from a wide range of other causes , including suicide . About 5 % of people with anorexia die from complications over a ten-year period , a nearly 6 times increased risk . The term anorexia nervosa was first used in 1873 by William Gull to describe this condition .