All the "named" dietary programs are likely to yield the same 6-kg weight loss at 1 year, so patients should be encouraged to follow whichever one they are most likely to adhere to, according to a report published online Sept. 2 in JAMA.
Despite advertising claims that certain named diets are superior to others, there have been very few head-to-head comparison studies, and none have had adequate numbers to achieve a definitive conclusion. In addition, no studies that have pooled the sparse available data have used rigorous meta-analytic techniques to allow quantitative comparisons among the diets, said Bradley C. Johnston, Ph.D., of the Hospital for Sick Children Research Institute, Toronto, and his associates.
©wragg/iStockphoto.com
All the dietary programs were likely to yield the same 6-kg weight loss at 1 year.
The investigators performed a network meta-analysis that included all available data from 48 randomized clinical trials (7,286 participants) to estimate the relative effects of three low-carbohydrate diets (Atkins, South Beach, and Zone), two low-fat diets (Ornish and Rosemary Conley), and five moderate-macronutrient diets (Biggest Loser, Jenny Craig, Nutrisystem, Volumetrics, and Weight Watchers). "We included dietary programs with recommendations for daily macronutrient, caloric intake, or both for a defined period (12 weeks or longer), with or without exercise (e.g., jogging, strength training) or behavioral support (e.g., counseling, group support). Eligible programs included meal replacement products but had to consist primarily of whole foods and could not include pharmacologic agents," they said.
All the diets were superior to no diet and all showed an approximate 8-kg weight loss at 6 months with a regain of approximately 2 kg at 12 months. "Although statistical differences existed among several of the diets, the differences were small and unlikely to be important to those seeking weight loss," Dr. Johnston and his associates said (JAMA 2014 Sept. 2 [doi:10.1001/jama.2014.10397]).
"Because different diets are variably tolerated by individuals, the ideal diet is one that is best adhered to by individuals so that they can stay on the diet as long as possible," the investigators noted.
Only 5 of the 48 trials reported on adverse events, and only 1 of them directly compared adverse events between low-carbohydrate against low-fat diets. That study found all adverse events to be more common with low-carbohydrate diets, including constipation (68% vs 35%), headache (60% vs 40%), halitosis (38% vs 8%), muscle cramps (35% vs 7%), diarrhea (23% vs 7%), general weakness (25% vs 8%), and rash (13% vs 0%).