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Comparison of Weight Loss Among Named Diet Programs in Overweight and Obese Adults: A Meta-Analysis
Study Questions:
Is weight loss similar among popular diets, based on macronutrient composition and named diet?
Methods:
This meta-analysis identified randomized controlled trials (RCTs), which reported weight loss of body mass index (BMI) reduction. A literature search of electronic databases including AMED, CDSR, CENTRAL, CINAHL, EMBASE, and MEDLINE, from inception of each database to April 2014, was used to identify 20,835 abstracts, and/or titles of interest. From this, 48 RCTs were included. Criteria for inclusion were an RCT with overweight or obese adults (BMI ≥25 kg/m2) randomized to a popular self-administered named diet and which reported weight or BMI data at follow-up. Only those studies with at least 3 months of follow-up were included. A Bayesian framework was used to perform a series of random-effects network meta-analyses with meta-regression to estimate the relative effectiveness of diet classes and programs for change in weight and BMI from baseline. The analyses adjusted for behavioral support and exercise. The primary outcomes of interest were weight loss and BMI at 6- and 12-month follow-up.
Results:
From the 48 unique RCTs, a total for 7,286 individuals were included (median age, 45.7 years; median weight, 94.1 kg; and median BMI, 33.7 kg/m2). The median duration of the diet intervention across the trials was 24 weeks (interquartile range, 16-52 weeks). The largest weight loss was associated with low-carbohydrate diets: 8.73 kg (95% confidence interval [CI], 7.27-10.20 kg at 6-month follow-up and 7.25 kg (95% CI, 5.33-9.25 kg) at 12-month follow-up, and low-fat diets: 7.99 kg (95% CI, 6.01-9.92 kg at 6-month follow-up and 7.27 kg (95% CI, 5.26-9.34 kg) at 12-month follow-up. Weight loss differences between individual diets were minimal. The Atkins diet resulted in a 1.71 kg greater weight loss than the Zone diet at 6-month follow-up. Between 6- and 12-month follow-up, the influence of behavioral support (3.23 kg [95% CI, 2.23-4.23 kg] at 6-month follow-up vs. 1.08 kg [95% CI, −1.82 to 3.96 kg] at 12-month follow-up) and exercise (0.64 kg [95% CI, −0.35 to 1.66 kg] vs. 2.13 kg [95% CI, 0.43-3.85 kg], respectively) on weight loss differed.
Conclusions:
The authors concluded that significant weight loss was observed with any low-carbohydrate or low-fat diet. Weight loss differences between individual named diets were small. This supports the practice of recommending any diet that a patient will adhere to in order to lose weight.
Perspective:
These data support the use of patient preference rather than one particular diet, particularly when choosing low-carbohydrate diets versus low-fat diets. Of note, the authors found behavioral support and exercise to enhance weight loss, suggesting that clinicians should council patients to include exercise and a behavioral program, if available.
Keywords: Body Mass Index, Weight Loss, Bayes Theorem, Obesity, Diet, Reducing, Diet, Fat-Restricted, Patient Preference
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