Dieting and the development of eating disorders

Nutrition Research Newsletter, Sept, 2004

America is experiencing an epidemic of obesity. Sixty four percent of adults are either overweight or obese, and the rates are only expected to rise in the next decade. As a result, the US Surgeon General and several government agencies have called for increased efforts to treat obesity, as well as to prevent its occurrence. Some investigators believe that dieting, defined as intentional caloric restriction to reduce body weight, is associated with the development of eating disorders. Young women, in particular, often diet aggressively in pursuit of an ever-thinner ideal. Whereas aggressive dieting clearly may be associated with ill effects in persons of average weight, the relevance of these findings to obese individuals who wish to lose weight through modest caloric restriction is not clear. The present study assessed whether caloric restriction would elicit binge eating in obese individuals who were free of this complication before treatment.

The researchers assessed the effects of a traditional 1200 kcal/d to 1500 kcal/d reducing diet comprising conventional foods, as well as of a 1000 kcal/d diet that included four servings daily of a liquid meal replacement. The latter diet was included because of concerns that low-calorie and very-low-calorie liquid diets, in particular, precipitate binge eating. Changes in these two groups in eating behavior, as well as mood, self-esteem, and body image, were compared with those in a third condition in which participants were instructed not to diet. Participants were 123 women with a mean ([ or -] SD) age of 44.2 [ or -] 10.0 y, weight of 97.3 [ or -] 13.0 kg, height of 164.3 [ or -] 6.4 cm, and BMI of 35.9 [ or -] 4.5.

The 123 participants were randomly assigned to one of the three conditions: 1) balanced-deficit diet (BDD; n = 43); 2) meal replacement plan (MR; n = 41); or 3) nondieting approach (ND; n = 39). All participants attended weekly group treatment sessions during the first 20 wk and every-other week sessions during weeks 22 to 40. Group sessions lasted 90 min, included 7 to 10 participants, and were led by a clinical psychologist. A registered dietitian co-led six sessions in each of the three treatment conditions. After week 40, participants attended follow-up group sessions at week 52 and week 65.

At week 20, participants in the MR, BDD, and ND groups lost 12.1 [ or -] 6.7%; 7.8 [ or -] 6.0%; and 0.1 [ or -] 2.4% of initial weight, respectively. Weight changes of participants in the three groups were generally consistent with their prescribed caloric intakes. During the first 20 wk, there were no significant differences among groups in the number of persons who had objective binge episodes or in reports of hunger or dietary disinhibition. Symptoms of depression decreased significantly more in the MR and BDD groups than in ND participants. At week 28, significantly more cases of binge eating were observed in MR participants than in the 2 other groups. No differences, however, were observed between groups at weeks 40 or 65 (a follow-up visit). At no time did any participant meet criteria for binge-eating disorder.

Before treatment, 67% to 77% of women in the three groups were judged to have had no episodes of subjective binge eating in the prior 28 d. On average, participants (across the 3 groups) had engaged in this behavior 1.3 [ or -] 4.2 d of the previous 28 d. At no time were there significant differences among groups in the number of days on which subjective binge episodes were reported. The number of participants in all conditions who experienced subjective binge episodes declined during the first 9 wk of treatment (as did the number of days to a mean of 0.2 [ or -] 0.6 d) but then returned toward baseline levels at week 20. There were no significant differences among groups at anytime during the study in the number of cases of subjective binge episodes. Contrary to the hypotheses, neither disinhibition nor hanger increased significantly in the MR or BDD conditions during caloric restriction.

This is the first prospective, randomized trial that was designed specifically to assess whether dieting is associated in obese individuals with the precipitation of binge eating and related behavioral complications. The researchers found no evidence during the first 20 wk of treatment that either a 1000 kcal/d diet, which included a liquid MR, or a 1200-1500 kcal/d diet, which comprised conventional foods, was associated with binge eating or other disordered eating. Moreover, neither of these diets was associated during this time, with increases in hunger, dietary disinhibition, or symptoms of depression. On the contrary, women who consumed either the MR or BDD reported significantly greater reductions in symptoms of depression than did participants in the ND condition. Women in all three treatment groups experienced decreases in hunger and disinhibition. The strength of the present findings resides in the selection of a well-defined sample (known before treatment to be free of objective binge episodes and depression), in the randomization of participants to dietary conditions, and in the frequent assessment of eating behavior by blinded examiners who used consistent criteria to judge binge episodes.