Eating disorders, such as anorexia, bulimia, and binge eating disorder, are associated with extreme emotions, attitudes, and behaviors, as well as physical problems that can have life-threatening consequences. These consequences are affecting adolescents with increasing frequency. Adolescent obesity is one of the risk factors for the development and maintenance of eating disorder symptoms[1–5]. One possible reason for this may be that overweight adolescents show greater concern about body image and a greater tendency to perform dietary restraint than their counterparts with normal weight. A number of studies have identified the association of increased risk for eating disorder symptoms with elevated weight and shape concerns, and unhealthy weight loss behaviors in overweight adolescents[1, 6–10].
A recent review on the epidemiology of eating disorders in Western countries indicated that the prevalence rates for anorexia nervosa ranged from 0.1% to 5.7% in females, and for bulimia nervosa from 0% to 2.1% in males and from 0.3% to 7.3% in females. The prevalence in non-Western countries for bulimia nervosa ranged from 0.46% to 3.2% in female subjects. Several school-based studies in China have reported the prevalence of eating disorders varied from 1.3% to 5.21% among females aged 15 to 24 years old[12–16]. However, due to the lack of a national epidemiological investigation in China, these data are not representative of the entire population.
Another public health concern related to weight is the high prevalence of weight control concerns and behaviors among adolescents. These concerns and practices are on a continuum ranging from healthy to unhealthy. Many overweight and obese adolescents display elevated risk for weight/shape concerns and dieting attempts which, in turn, are associated with disturbance in eating habits. Longitudinal studies have found that weight and shape concern and weight control behaviors are potent predictors for future onset of full- and sub-threshold anorexia nervosa and bulimia nervosa[17–20]. Population-based studies showed that half of adolescent girls and one third of adolescent boys reported unhealthy weight control behaviors such as dieting and excessive exercise, and 7-12% of adolescent girls and 3-7% of adolescent boys tried to lose weight by extreme behaviors such as vomiting, taking diet pills, or laxatives[21–26]. To date, little is known about the prevalence of weight control concerns and behaviors in Chinese population.
Previous studies of associations between body weight, weight control concerns and practices, and eating disorder symptoms have included measures of BMI, weight control concerns and practices or eating disorder symptoms but, to this point, all three measures have not been systematically investigated within a single study[1, 6, 25, 27–33]. Therefore, the independent effects of BMI and weight control concerns and practices on eating disorder symptoms are not clear. BMI and weight control concerns and practices may each have a direct or indirect association with eating disorder symptoms.
Based on the evidence that elevated adiposity is theorized to contribute to weight control concerns and behaviors among adolescents [34–39] and that weight/shape concern and weight control behaviors increases risk for the onset and maintenance of eating disorders symptoms[7, 28, 31, 40], we hypothesized that weight control concerns and behaviors may mediate the association between BMI and eating disorder symptoms. Given the rather limited literature concerning the role of weight control concerns and behaviors among non-clinical Chinese adolescents, the current study tested this hypothesis using a national representative survey of adolescents.
The purpose of this study are: firstly, to investigate the prevalence of overweight or obesity, weight control concerns and behaviors, and eating disorder symptoms in a population of non-clinical Chinese adolescents; secondly, to study whether BMI category, or weight control concerns and behaviors significantly contribute to eating disorder symptoms either individually, or in concert; and lastly, to determine if weight control concerns and behaviors will mediate the association of BMI category and eating disorder symptoms.