Choosing Among Diets Did Not Improve Weight Loss

William S. Yancy, Jr., MD, MHSc Research Associate Center for Health Services Research in Primary Care Durham, NC 27705 Associate Professor Department of Medicine Duke University Medical Interview with:
William S. Yancy, Jr., MD, MHSc
Research Associate
Center for Health Services Research in Primary Care
Durham, NC  27705
Associate Professor Department of Medicine
Duke University Medical Center

Medical Research: What is the background for this study? What are the main findings?

Dr. Yancy: A number of studies have compared different diet approaches for weight management with many of these finding that several different diets can result in significant weight loss. This has led many experts to advise that we should offer a choice among these diet options to our patients who are seeking to lose weight. We know that adherence is the best predictor of weight loss during dietary interventions, so the thought is that patients will adhere better to a diet that they prefer, resulting in more successful weight loss. In addition, allowing choice enhances patient autonomy, which is patient-centered and has been shown to increase treatment adherence. However, the previous studies of various diet approaches did not let people choose a diet, so we don’t actually know if letting them choose will lead to better weight loss. Our study specifically tested this assumption. We randomized participants to a condition where they were allowed to choose between 2 common weight loss diets or to a condition where they were randomly assigned to one of the diets. The 2 diets we used were a low-carbohydrate diet without calorie restriction and a low-fat diet combined with calorie restriction. Participants received counseling about the diets, and about behavioral strategies and physical activity, in 19 group sessions over the span of 12 months. They also received 6 phone calls with motivational counseling in the latter half of the program.

Medical Research: What should clinicians and patients take away from your report?

Dr. Yancy: The surprising result was that the opportunity to choose among diets did not help weight loss. Nor did it improve attendance at counseling sessions, self-reported adherence to diet or even weight-related quality of life. An interesting finding was that, among patients who were able to choose a diet, more chose the low-carbohydrate diet. Because the patient sample was composed of veterans, about 70% were men, who might prefer foods that are emphasized with a low-carbohydrate diet. Another interesting finding was that only 5 patients who got to choose their diet switched to the other diet when given the opportunity after 12 weeks on their first choice diet. We chose 12 weeks for this potential change to give patients ample opportunity to learn their first choice diet and minimize switching when the original diet was actually a good fit. Nevertheless, we were surprised to see only 5 patients took the opportunity to switch even though there were more who were struggling at that point. The results are important because it may be that some people will choose a diet based on their food preferences but their preference for those foods might make it difficult for them to scale down on the amount that they eat.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Yancy: Future research might consider matching the most effective diet to an individual using other patient characteristics such as metabolic profile or even genetic profile.


Effect of Allowing Choice of Diet on Weight Loss: A Randomized Trial

William S. Yancy Jr., MD; Stephanie B. Mayer, MD; Cynthia J. Coffman, PhD; Valerie A. Smith, DrPH; Ronette L. Kolotkin, PhD; Paula J. Geiselman, PhD; Megan A. McVay, PhD; Eugene Z. Oddone, MD; and Corrine I. Voils, PhD

Ann Intern Med. 2015;162(12):805-814. doi:10.7326/M14-2358

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Last Updated on June 18, 2015 by Marie Benz MD FAAD