Allowing obese patients to choose between a low-carbohydrate or a low-fat diet according to their food preferences did not enhance their weight loss, dietary adherence, or weight-related quality of life, compared with randomly assigning them to one of the diets, according to a report published online June 15 in Annals of Internal Medicine.
Several studies have suggested that offering patients a choice among evidence-based dietary strategies for losing weight would facilitate their adherence and thus improve their results.
Researchers studied a 1-year weight-loss intervention among 207 overweight/obese adults (mean body mass index 36 kg/m2) who completed the Geiselman Food Preference Questionnaire to determine whether their preferences for 72 common foods aligned better with a low-carbohydrate or a low-fat diet.
Among the study participants, 105 were allowed to choose a low-carbohydrate or a low-fat diet, and 102 were randomly assigned to those diets. Mean age of the participants was 55 years; 73% were men; and 51% were African American.
All the participants received verbal and printed information about the efficacy and safety of the diets; sample menus; and a pocket guide to counting calories, fats, and carbohydrates. All were offered up to 19 group counseling sessions and individual telephone counseling from the study dietitian, and all were encouraged to aim for 30 minutes of moderate-intensity aerobic physical activity 5 days per week, said Dr. William S. Yancy Jr. of the Durham (N.C.) Veterans Affairs Medical Center and the VA’s Center for Health Services Research in Primary Care, and his associates.
Dietary adherence was similar between the two study groups. At final follow-up, the estimated mean weight loss for patients who chose their diet was 5.7 kg, or 5.6%, of their baseline body weight, compared with 6.7 kg, or 6.2%, of their baseline body weight, for patients who were assigned to a diet.
Final waist circumference and BMI were not significantly different between the two study groups, nor were scores on two measures of quality of life. “Contrary to expectations, the opportunity to choose a diet did not improve weight loss,” the investigators said (Ann. Intern. Med. 2015 June 15 [doi:10.7326/M14-2358]).
The findings indicate that providing a choice of diets may actually hinder weight loss, the researchers noted.
“One reason may be that persons are more likely to overeat when following a diet that emphasizes foods they find palatable,” Dr. Yancy and his associates explained. “Another reason may be a ‘personal trainer’ effect, in which persons may be more adherent to a fitness program if directed on what exercises to do rather than choosing their own.”
The U.S. Department of Veterans Affairs funded the study. Dr. Yancy reported receiving personal fees from Nutrisystem and the University of Pennsylvania.