1. Low carbohydrate and low fat diets yielded the greatest amount of weight loss at 6 and 12 months when compared to other diet strategies in this meta-analysis.
2. Of the 11 named diets included in this meta-analysis, the Atkins diet achieved the best weight loss at 6 months and at 12 months the Ornish, Rosemary Conley, Jenny Craig, and Atkins diets were comparable.
Evidence Rating Level: 2 (Good)
Study Rundown: In the last several years many named diets, such as the Atkins and Jenny Craig diets, have become popular. This meta-analysis of 48 studies compared the various dietary strategies and named diets to investigate any differences between them. The primary outcomes were weight loss at 6 and 12 months. At both time points, any diet was superior to no diet, and this difference was 1-2 pounds greater at 6 months than at 12 months. At 6 months, low carbohydrate and low fat diets appeared to be equally effective and more effective than other diet strategies. At 12 months, the low carbohydrate and low fat diets continued to be the most effective. At 6 months, the largest weight loss was achieved with the Atkins diet, followed by the Volumetrics diet, followed by the Ornish diet. All named diets included in the study except for the Jenny Craig diet had a greater effect at 6 months than 12 months.
Strengths of this study include the stringent inclusion criteria and the assessment for publication bias. One important weakness of the study is the use of a network meta-analysis, which compares diets that were never actually compared in a single study. Ultimately, this paper suggests that low carbohydrate and low fat diets achieve the best results and underscores the importance of selecting a dietary strategy that will be manageable for the individual attempting to lose weight.
Click to read the study, published today in JAMA
Click to read an accompanying editorial in JAMA
Relevant Reading: Evaluating commercial weight loss programmes: an evolution in outcomes research
In-Depth [meta-analysis]: This network meta-analysis of 48 studies compared various weight loss strategies and named diets to determine which diets achieve the greatest amount of weight loss at 6 and 12 months. When compared to no diet 6 months, low carbohydrate diets had a mean difference in weight loss of 8.73 kg (95% CI 7.27-10.20) and low fat diets had a mean difference in weight loss of 7.99 kg (95% CI 6.01-9.92). The low carbohydrate and low fat diets achieved greater weight loss than other diet types. Low carbohydrate diets and low fat diets continued to perform the best at 12 months with 7.25 kg (5.33-9.25) and 7.27 kg (95% CI 5.26-9.34) greater weight loss than no diet, respectively. At 6 months, the Atkins diet achieved the greatest amount of weight loss among the 11 named diets included in the study in comparison to no diet [10.14 kg (95% CI 8.19-12.12)]. All diets except for Jenny Craig had a smaller effect at 12 months than 6 months. At 12 months, the Ornish, Rosemary Conley, Jenny Craig, and Atkins diets were associated with the greatest amount of weight loss, and weight loss at 12 months ranged from 6.35-6.55 kg in those diets when compared to no diet.
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