Comparison of Atkins, Zone, Ornish, and LEARN Diets in Overweight Premenopausal Women...
A new study(1) reports the results of a year-long study of the effects on weight loss among four diets: the Atkins (77 subjects), Zone (79 subjects), Ornish (76 subjects), and LEARN (79 subjects). As you are undoubtedly aware, the Atkins diet is very low in carbohydrates. The Zone diet is low in carbohydrates, the LEARN diet is low in fats and high in carbohydrates, and the Ornish diet is very high in carbohydrates and very low in fats.
The summary of the results reported that “. . . premenopausal overweight and obese women assigned to follow the Atkins diet, which had the lowest carbohydrate intake, lost more weight and experienced more favorable metabolic effects at 12 months than women assigned to follow the Zone, Ornish, or LEARN diets.”
The mean 12-month weight losses were: Atkins, –4.7 kg (95% confidence interval, –6.3 to –3.1 kg); Zone, –1.6 kg (95% confidence interval, –2.8 to –0.4 kg); LEARN, –2.6 kg (–3.8 to –1.3 kg); and Ornish, –2.2 kg (–3.6 to –0.8 kg). The mean weight losses were significantly different between the Atkins and Zone diets, whereas weight losses were not statistically different among the Zone, LEARN, and Ornish groups. Dietary intakes were determined by telephone-administered, 3-day, unannounced, 24-hour dietary recalls. Energy expenditure was estimated by using the “well-established” Stanford 7-day physical activity recall. Hence, results were limited by potential biases in recall of dietary intakes and of physical activity.
It is interesting to note that the diets were all low in fiber. Calculated fiber contents of the diets at 12 months were: Atkins, 15.2 (±2.7); Zone, 16.7 (±9.4); LEARN, 18.3 (±7.8); and Ornish, 19.3 (±9.4). The fiber content of those on the Ornish diet was significantly different from that of those on the Atkins diet.
The Atkins diet was significantly higher in fat (44.3 ± 12.5, up from 36.2 ± 7.8 at baseline) at 12 months than the other diets, while protein content of the Ornish diet (18.3 ± 4.0) was significantly lower than that of the Atkins diet (20.6 ± 5.3). The Atkins diet was also significantly higher in saturated fat content (27.2 ± 13.3, up from 26.5 ± 11.1 at baseline) than the other three diets. Interestingly, the Ornish group was only able to get their saturated fat percentage down from 24.8 ± 10.3 at baseline to 16.9 ± 11.4, although the goal was to reach 10% or less saturated fat. This underscores the difficulties for individuals trying to reduce saturated fat to such a low level.
Insulin and glucose measurements showed that neither the overall trajectory across all time points nor the 12-month differences were significantly different among the groups, either for fasting insulin or fasting glucose. HDL-cholesterol was significantly greater (compared to baseline) at 12 months in the Atkins, Zone, and LEARN diets as compared to the Ornish diet. Diastolic blood pressure was significantly lower (compared to baseline) in the Atkins, Zone, and LEARN diets as compared to the Ornish diet. Systolic blood pressure was significantly lower (compared to baseline) in the Atkins diet as compared to the other three diets.
This study provides clear supporting evidence for the benefits of reducing carbohydrate calories for weight loss (Atkins diet) and also demonstrates favorable changes for those on the Atkins diet in lipid levels and blood pressure.
Reference
Gardner et al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women. JAMA 297(9):969-77 (2007).
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Comment: While I like the Atkins diet, I have refined these and other successful concepts to a much better overall approach to long term weight loss and improved health & wellness.
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Christopher Wiechert, C.N.C.
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