New Study Compares Four Popular Diets
posted 01/05/05

Tomorrow’s Journal of the American Medical Association reports the results of a head-to-head comparison of four popular diets: Atkins, Ornish, Weight Watchers, and the Zone. Tufts University researchers randomly assigned 160 people to the four diets, gave them an instruction book and four educational sessions, and then tracked their weight over the next year. After the first two months, participants were encouraged to follow their assigned diets only insofar as they felt inclined to.

At the one-year mark, the average weight loss was 3.3 kg (7.3 lb) for Ornish, 3.2 kg (7.0 lb) for the Zone, 3.0 kg (6.6 lb) for Weight Watchers, and 2.1 kg (4.6 lb) for Atkins. These numbers are group averages, including both compliant and noncompliant dieters; weight loss was greater for those who continued to follow their diets. About half of the Ornish and Atkins dieters and two-thirds of the Weight Watchers and Zone dieters reported continuing to follow their regimens over the entire year.

Low-density lipoprotein (“bad”) cholesterol dropped by 12.6 percent in the Ornish group, 11.8 percent for the Zone group, 9.3 percent for the Weight Watchers group, and 7.1 percent for the Atkins group at one year.

Dansinger ML, Gleason JA, Griffith JL, Selker HP, Schaefer EJ. Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction. JAMA 2005;293:43-53.

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