Dieting and Connections to Eating Disorders

Some believe that dieting may lead to development of eating disorders. For example, in the vast number of cases, dieting precedes the onset of binge eating.

Dr. Thomas A. Wadden and co-workers at the University of Pennsylvania School of Medicine, Philadelphia, recently designed a study to examine whether dieting could lead to development of binge eating and disturbance of mood (Am J Clin Nutr 2004; 80:560). The 123 women who participated in the study were randomly assigned to one of three conditions: a balanced deficit diet, a meal replacement plan, or a non-dieting approach.

Balanced deficit diet group

The first group was instructed to consume a self-selected balanced deficit diet of from 1200-1500 kcal/day (approximately 15% of calories from protein, 30% or fewer calories from fat, and the remainder from carbohydrate). In this group, participants received a copy of the LEARN Program for Weight Control, and completed daily food records. They could eat any foods they wished, provided they adhered to their weight-loss goals. Treatment sessions also reviewed behavioral weight-control topics. The women were encouraged to walk or engage in other aerobic activity for 150 minutes per week by the end of week 20, with an increase to 180 minutes per week by week 40. Participants also kept an activity diary.

Meal replacement group

Women in the meal replacement group received the same treatment as those in the balanced-deficit diet group, with one major difference. From week 2 through week 13, the women were prescribed a 1000-kcal/day meal replacement plan that consisted of 4 servings of a liquid diet (OPTIFAST 800), combined with an evening meal of a frozen food entrée, a serving of fruit, and a green salad. Each serving of the liquid diet provided 160 kcal, with 14 g protein, 20 g carbohydrate, and 3 g fat. Beginning at week 14, participants gradually cut back on the liquid diet, and by week 17 they were prescribed a 1200-1500 kcal/day diet of conventional foods, just as the women in the first group. The meal replacement plan was included to ensure that at least one group of participants had marked caloric restriction.

Non-diet group

Women in the third group were carefully instructed not to reduce their caloric intake. To encourage the women to give up dieting, participants began the program by listing all the diets they had tried, the number of pounds they had lost and regained, and then were asked to calculate what they had spent on these efforts. At week 6, the women were encouraged to adopt a new eating plan: they were to eat at least every 4 hours to avoid becoming hungry, to eat whatever food they wanted, eliminating the idea of “bad” foods that should be avoided, and to stop eating when they felt full.

Registered dietitians provided women in this group with the same 6 lectures on healthy eating that the women in the other groups had. Women in the third group were also instructed to increase their physical activity by the same number or minutes per week as those in the other two groups. The non-dieting group also received instruction about improving self-esteem and body image as well as living more fulfilling lives regardless of their weight.

No connection to binge eating found

The researchers found no evidence during the first 20 weeks of treatment that either a 1000 kcal/day diet, which included a liquid meal replacement, or a 1200-1500 kcal/day diet or conventional foods was associated with binge eating or other disordered eating. Neither of these diets was linked to increases in hunger, dietary disinhibition or symptoms of depression. In contrast, women who were either in the meal-replacement or balanced deficient diet reported significantly greater reductions in symptoms of depression than did participants in the non-dieting group. Women in all three treatment groups had decreased hunger and disinhibition. Although there were no differences between groups at week 40 and at the 65-week follow-up visit, at week 28 significantly more cases of binge eating were observed in the meal replacement group than in the two other groups.

Which dieters are vulnerable?

If dieting is a precipitating factor in vulnerable individuals, who can predict who is vulnerable or not? In a longitudinal study of London schoolgirls (31% of whom were dieting), about one-fifth of the dieters progressed to an eating disorder during a 12-month period of observation. These results correspond to an eightfold increase in the risk for meeting diagnostic criteria for an eating disorder in dieters vs., nondieters. Among the dieters, those individuals subsequently diagnosed with an eating disorder had an increased in self-reported depressive symptoms compared with the dieters who did not develop an eating disorder. Depression was the only factor that discriminated between outcomes (Ann Med 1992; 24:2811)

Anecdotal observations and one research report have suggested that liquid diets, and very-low-calorie diets that provide less than 800 kcal/day may be associated with binge eating, particularly after patients begin eating conventional foods once more. Five women in the meal-replacement group experienced one or two episodes of binge eating in the month before their week 28 assessment. No objective binge eating episodes were noted at week 40.

The authors believe that the that findings of the adverse effects of dieting in persons of average weight or those with bulimia nervosa or anorexia nervosa have in some instances been inappropriately generalized to overweight and obese individuals who try to lose weight by restricting calories. They also believe that concerns about the possible adverse effects of dieting should not dissuade overweight and obese persons from attempting to lose weight. The health benefits of modest weight loss and increased physical activity are extremely compelling, according to Dr. Wadden and colleagues.