Eating disorders are an increasing public health problem among young women: they may give rise to serious physical problems such as hypothermia, hypotension, electrolyte imbalance, endocrine disorders and kidney failure. Women with eating disorders are also at risk of long-term psychological and social problems, including depression, anxiety, substance abuse and suicide. The costs in terms of quality of life, loss of productivity, serious medical problems and mortality are high. 
Clinical eating disorders include anorexia nervosa and bulimia nervosa.  Anorexia is characterized by a severely calorie-restricted diet, resulting in a body weight that is at least 85% below that expected for age and height.  Bulimia is identified by frequent fluctuations in weight and recurrent episodes of compulsive bingeing followed by self-induced vomiting, purging, fasting, laxative use and/or excessive exercise in attempts to avoid weight gain. Eating disorders not otherwise specified include behaviours such as chronic dieting, purging and binge-eating, which do not meet the full criteria for a specific eating disorder, they are two to five times as common as the clinical eating disorders.
Eating disorders are, by and large, a problem among women. From the data collected in the Ontario Health Survey, Mental Health Supplement, the lifetime prevalence of bulimia (according to the criteria of the Diagnostic and Statistical Manual, 3rd revision [DSM-III-R]) among women aged 15 to 65 was estimated as 1.1% in 1990. In 1995, 95% of reported hospitalized cases of anorexia and more than 90% of hospitalized cases of bulimia in Ontario were women.
In addition to eating disorders, preoccupation with weight and body image, and self-concept disturbances, are more prevalent among women than men.[4, 6–9] Personal, behavioural and socio-environmental factors, such as negative body image, low self-esteem, fear of becoming fat, chronic dieting and social pressures to be thin, are identified risk factors.[1, 6, 10–13]
Body image concerns and preoccupation with body weight and shape increase as girls become older and more aware of the idealized societal preference for a thin body shape. The images of women in the media and popular culture place pressure on vulnerable young girls and women to live up to these expectations, regardless of their natural body shape.[8, 9] In British Columbia, it was found that by age 18, 80% of girls at all weights reported that they would like to weigh less.[15, 16] A school-based population study involving 1,739 adolescent women aged 12 to 18 years in Toronto, Hamilton and Ottawa found that current dieting to lose weight was reported by 23% of participants, binge-eating by 15%, self-induced vomiting by 8.2% and the use of diet pills by 2.4%.
Body shape dissatisfaction and preoccupation with weight are not limited to adolescents but also occur in children. A recent Canadian school-based study concluded that 34% of prepubescent girls, 36% of early pubescent girls and 76% of post-pubescent girls were dissatisfied with their body shape. In a survey of eating and smoking behaviours among boys and girls in grades 4 to 8 in southwestern Ontario and Charlottetown, more than 25% from each grade reported not eating breakfast every day, and there was a sharp increase among girls beginning in grade 7. Unhealthy eating patterns in childhood can adversely affect health, contribute to chronic disease in later life, and often persist into adolescence and adulthood, since change is difficult once eating patterns are established.
The starvation associated with anorexia and the chronic vomiting frequently associated with bulimia can cause serious medical problems, such as hypothermia, hypotension, anemia, osteoporosis, endocrine abnormalities, dehydration, kidney stones, metabolic alkalosis and dental caries. Girls and women with eating disorders are also at increased risk of menstrual irregularities such as amenorrhea, infertility, [19, 20] miscarriages and fetal complications such as prematurity, low birth weight, malformations and low Apgar scores.[1, 20–23]
Mothers who have or have had an eating disorder may also create abnormal behavioural patterns when feeding their children, such as irregular feeding schedules, detached non-interactive mealtimes, and use of food for non-nutritive purposes, which may lead to second-generation eating problems. [24–27]
In addition to depression, anxiety and obsessive-compulsive disorders, eating disorders are also associated with diminished libido, altered sleeping patterns, irritability and suicide attempts.[3, 28, 29] Ontario women with bulimia have higher levels of anxiety, depression and alcohol abuse than those without bulimia.[3, 4, 29, 30] Smoking and substance abuse are much more prominent among teenaged girls with eating disorders than among those with healthy eating habits. [3, 17, 28] In a recent analysis of the 1997 Ontario Student Drug Use Survey, adolescent females who perceived themselves as overweight were almost 50% more likely to smoke than those who considered themselves of average weight or too thin, whereas weight perceptions were not associated with smoking among males. Several studies have suggested an association between a traumatic experience (sexual or physical abuse) and later self-injury. A recent study found that among patients with eating disorders there is a more than 30% lifetime risk of self-injurious behaviour.
The rate of death from anorexia is higher than from bulimia because of the complications of starvation and electrolyte imbalances, or suicide.[33, 34] A recent review reported a mortality rate of 0.6% for anorexia as compared with 0.3% for bulimia. A longitudinal U.S. study (21-year follow-up) of 84 women with anorexia reported that 14 women (16.7%) had died, and 12 of the 14 had died of causes directly related to anorexia; the observed death rate was 9.8 times greater than expected.
Although previous studies in Canada and the United States have demonstrated differences in education and socio-economic status (SES) in the prevalence of obesity, [36–38] the relation between eating disorders and SES is still unclear.[17, 39] Jones et al observed that SES was not significantly associated with disturbed eating behaviours in a school-based Ontario population (n = 530), findings that are consistent with those of previous studies and may reflect the pervasive influence of the media on all SES groups.
Cultural beliefs and attitudes are identified as significant contributing factors in the development of eating disorders. Canadian research on eating disorders and ethnic background, however, is extremely limited.
A few studies propose that cultural beliefs may actually protect ethnic groups against eating disorders, but their effect may be eroded as adolescents face pressures of acculturation. A recent study of Mexican-American women across generations reported that second-generation women displayed the most disordered eating patterns and the highest degree of acculturation to mainstream U.S. culture. Experiences of cultural change (such as those of immigrants, for example) may also increase vulnerability to eating disorders.[43, 44]
This study presents data from the NPHS and national databases to investigate the burden of eating disorders in Canada and to explore the differences in attitude to weight between men and women.