Dieting: Good or Bad?

Given the current obesity epidemic, it is important to determine the extent to which individuals should be encouraged to diet. Dieting is already quite common in the general population, but it has variable effectiveness, depending on the weight-control behaviors that are used. Questions abound about the usefulness of dieting as well as its influence on medical and psychiatric health. The controversy that surrounds dieting may in part be due to confusion between dieting and the construct of restraint. Dieting is not considered to be synonymous with restraint, as described by Peter Herman and Janet Polivy. (Recent research indicates that items on their Restraint Scale do not measure dietary behaviors or restrained eating per se, and most “restrained eaters” who the scale identifies do not report currently dieting to lose weight.) Determining how “good” or “bad” dieting is involves three central issues: the effectiveness of dieting, its physical or biological effects, and its psychological effects. The effectiveness and consequences of dieting depend largely on the type of dieting behaviors that are being used and who is using them. Context is critical for understanding how helpful or harmful dieting is.

Effectiveness of Dieting

Information is available about the effectiveness of several types of dieting: dieting programs that are researched at university clinics, commercial dieting programs, and self-guided (i.e., independent) dieting. The most information is available about dieting programs that are researched at university clinics. However, the participants who enroll in these programs likely differ in significant ways from typical dieters; individuals who seek treatment from university-based clinics have more psychiatric problems (e.g., depression or binge eating) and a longer history of unsuccessful dieting.

University clinics often offer comprehensive weight-control programs that promote weight loss through nutrition change (e.g., a calorie-restricted, low-fat diet) and physical activity. Behavioral treatment (e.g., teaching techniques such as self-monitoring, goal setting, and stimulus control) can facilitate these changes in diet and exercise. Group-based behavioral treatment is the gold standard for weight-loss dieting. This approach is effective in the short term. On average, it results in a loss of approximately 10 percent of initial body weight in approximately 30 weeks of treatment, which is considered a medically significant weight loss. However, weight-loss maintenance remains a challenge for virtually all approaches, including behavioral [Page 185]treatment: the majority of dieters regain lost weight within 3–5 years. As a consequence, obesity is increasingly being conceptualized as a chronic disorder that requires long-term care. When contact with treatment providers is continued (e.g., through group meetings or phone calls) weight regain is slowed. Development of dieting programs that have promising long-term results is a priority for future research.

Some research has also been conducted on the effectiveness of commercial dieting programs, which millions of Americans enroll in each year. Very-low-calorie diets (e.g., Optifast) can promote large weight losses (e.g., 15 to 20 percent of body weight), but weight-loss maintenance is poor. Purchasing meal replacements (e.g., SlimFast) for use in a balanced-deficit diet also can facilitate 5 to 10 percent weight losses; continued use of meal replacements also may facilitate weight-loss maintenance. Finally, group-based approaches such as Weight Watchers can be effective at producing weight loss of approximately 5 percent of initial weight.

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