Researchers from Stanford University Medical School assigned 311 pre-menopausal overweight and obese women (average age 41, average BMI 32 kg per sq. m) to follow one of four diets – Atkins (very low in carbohydrate), Zone (low in carbohydrate), Ornish (high in carbohydrate) and LEARN (low in fat, high in carbohydrate, based on national guidelines) - for one year.
The women received attended one-hour classes by registered dieticians once a week for eight weeks, and were responsible for preparing and buying all their own meals, and not everyone followed the diets exactly as the books described, just as in real life.
The study, funded by the National Institutes of Health and the Community Foundation of South-eastern Michigan, found that weight loss was highest in the women following the Atkins diet (4.7 kg, 10.4 lbs) compared to the Zone (1.6 kg, 3.5 lbs), LEARN (2.2 kg, 5.7 lbs), and Ornish (2.6 kg, 4.8 lbs).
Compared with women who were assigned to follow diets having higher carbohydrate content, women assigned to the diet with the lowest carbohydrate content had more weight loss and more favourable changes in related metabolic risk factors at two and six months.
Despite previous concerns over low carbohydrate diets adversely affecting blood lipid profiles, the current study did not report any such adverse effects on the lipid profiles of the pre-menopausal women within the 12-month study period.
It could not be determined whether the benefits of the Atkins diet were attributable specifically to the low carbohydrate intake versus other aspects of the diet (e.g. high protein intake).
While questions remain about long-term effects and mechanisms, a low-carbohydrate, high-protein, high-fat diet may be considered a feasible alternative recommendation for weight loss: weight loss is likely to be at least as large as for any other dietary pattern and the lipid effects are unlikely to be of immediate concern. As with any diet, physicians should caution patients that long-term success in weight loss requires permanent alterations in energy intake and energy expenditure, regardless of macronutrient content.
Source: Journal of the American Medical Association
7 March 2007, Volume 297, Pages 969-977
"Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women"
Authors: C.D. Gardner, A. Kiazand, S. Alhassan, S. Kim, R.S. Stafford, R.R. Balise, H.C. Kraemer, A.B. King
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