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July 11, 2007

Comparison of Weight-Loss Diets—Reply

JAMA. 2007;298(2):173-175. doi:10.1001/jama.298.2.174-b

In Reply: The A TO Z study was designed to test the 12-month effectiveness of popular weight-loss diets among 311 overweight or obese women. By design, the primary intervention was to read and follow assigned diet books. After 12 months, the Atkins group had a mean weight loss of 4.7 kg while the other 3 groups had mean losses of 1.6 to 2.6 kg. Drs McCarthy and Kuo as well as Drs Heymsfield and Blackburn suggest that poor adherence to the diets may have led to inadequate testing of the diets. Documenting adherence was a major priority, as evidenced by the resources committed to collecting 3137 dietitian-administered 24-hour recalls. However, attempting to enforce adherence, as one might do in a feeding study or other laboratory experiment, was not a study aim. Rather, the primary objective was to test the effectiveness of popular weight-loss diet books followed under free-living or “real-world” conditions. At 12 months, there were statistically significant group differences in macronutrient intakes and weight loss. Adherence was mediocre, reflecting real-world challenges with each diet book, despite optimization of program delivery via dietitian assistance in the first 8 weeks of the protocol. The development of methods to optimize adherence to weight-loss diets through increased use of behavior modification, improved physical activity strategies, and other approaches is a research priority.1

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