An examination of the relationships between obesity, weight loss diets and eating disorder behaviors

The occurrence of obesity with comorbid eating disorders is associated with increased risk for mental and physical health complications, however there are concerns that dietary obesity treatments may increase eating disorder behaviors, notably binge eating. Thus, the aims of this thesis were to investigate the prevalence of obesity with comorbid eating disorders, and to examine the effects of weight loss diets on eating disorders in individuals with obesity. Four studies were conducted to achieve these aims, and these are in Chapters 2-5. Chapter 2 is an epidemiological study that found an increase in the prevalence of obesity with comorbid eating disorder behaviors between 1995 and 2015. This increase in prevalence was greater than the increase in prevalence of either obesity or eating disorder behaviors separately. These findings indicate the need for integrated treatments for both conditions. Therefore, Chapter 3 is a pilot study of a simultaneous treatment for obesity with comorbid eating disorders, named HAPIFED (a Healthy APproach to weIght management and Food in Eating Disorders). This study showed the feasibility and acceptability of this treatment; nonetheless, weight loss was modest, and the effects on eating disorder behaviors of existing dietary obesity treatments that induce greater weight loss also need to be examined. Thus, Chapter 4 is a systematic review on the effects of severe dietary energy restriction – achieved via the use of very low energy diets – on binge eating in individuals with obesity. This study showed that clinically supervised very low energy diets mostly did not induce – and even reduced – binge eating in individuals with obesity. These findings were at odds with the trans-diagnostic cognitive-behavioral model of eating disorders, which suggests that strict dieting causes binge eating. For this reason, Chapter 5 is an examination of the applicability of this model to the general population. This study partially supported some of the relationships shown in the model in the general community, but found that the relationship between strict dieting and binge eating is small in the general population. The results from this thesis indicate that there is a growing prevalence of obesity with comorbid eating disorders, and weight loss diets mostly do not induce and can even reduce binge eating in individuals with obesity