Popular weight loss programs represent a multibillion dollar industry. A 2014 systematic review of 48 randomized control trials was conducted to compare weight loss outcomes with popular diets, such as Atkins, Weight Watchers, Ornish, Jenny Craig, Volumetrics, and Nutrisystem. Overweight or obese adult participants were randomized to a particular diet and were followed up with at 6 and 12 months. Of the 48 randomized control trials, 5 did not report weight loss at 6 months, and 23 trials did not report weight loss at 12 months (2).
At 6 and 12 months, low-fat and low carbohydrate diets resulted in the greatest weight loss compared to other diets, or no diet at all. Greatest weight loss at 6 months was seen with the Atkins diet (22.3 lbs), followed by the Volumetrics diet (21.7 lbs), and the Ornish diet (19.9 lbs). At 12 months, the Ornish, Rosemary Conley, Jenny Craig, and Atkins diets were associated with the greatest weight loss, at approximately 14 lbs. Although these diets were associated with the greatest weight loss at 6 and 12 months, approximately 2 to 4 lbs were regained by 12 months. In fact, all diets except Jenny Craig slightly decreased in their estimated effects at 12 months compared to 6 months (2).
The authors of this systematic review concluded, “Because different diets are variably tolerated by individuals, the ideal diet is the one that is best adhered to by individuals so that they can stay on the diet as long as possible” (2).
To this point, a randomized control trial included in this meta-analysis assessed adherence and effectiveness of the Atkins, Zone, Weight Watchers, and Ornish diet, for weight loss and cardiac risk factors. Participants had a mean age of 49 and BMI of 35. Only 93 of the 160 participants completed the study, indicating a high dropout rate of 42%. Attrition rates were highest amongst the more extreme diets, the Atkins diet at 48%, and the Ornish diet at 50% (1).
Although both the Atkins and Ornish diets resulted in modest, statistically significant weight loss (10.6 lbs for Atkins, 13.2 lbs for Zone, 10.8 lbs for Weight Watchers, and 16.1 for Ornish) and improved cardiac risk factors at 1 year, these diets had poor sustainability and adherence rates which resulted in weight regain and worsening cardiac risk factors for each diet group as a whole (1). The research also found a strong association between weight loss and self-reported dietary adherence, but not with weight loss and diet type. This underscores the concept that adherence level, rather than diet type, is the key determinant of clinical benefits (1).
Johnston et al. (2014) concludes, “The weight loss differences between individual named diets were small with likely little importance to those seeking weight loss.” There is no need for a one-size-fits-all approach to dieting. Diet adherence alone is the basis to having the greatest success at weight loss.
References
(1) Dansinger ML, Gleason JA, Griffith JL, Selker HP, Schaefer EJ. Comparison of Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction. JAMA 2005; 293(1): 43-53.
(2) Johnston BC, Kanters S, Bandayrel K et al. Comparison of weight loss among named diet programs in overweight and obese adults. A meta-analysis. JAMA. 2014; 312(9): 923-933.
Written by Nicole Lindel ~ Nutrition Education Master’s Student at Columbia University