Embargo expired: 6/8/2009 4:00 PM EDT
Source Newsroom: American Medical Association (AMA)
Newswise — Overweight individuals who ate a low-calorie, low-carbohydrate diet high in plant-based proteins for four weeks lost weight and experienced improvements in blood cholesterol levels and other heart disease risk factors, according to a report in the June 8 issue of Archives of Internal Medicine, one of the JAMA/Archives journals. A high-carbohydrate, low-fat vegetarian diet also resulted in weight loss but without the additional cardiovascular benefits.
"There is a dilemma relating to the proportion and source of fat, protein and carbohydrate that constitutes the optimal weight loss and cholesterol-lowering diet," the authors write as background information in the article. Newer dietary approaches for the prevention and treatment of chronic disease emphasize increased fruit and vegetable intake and reduced meat consumption.
However, low-carbohydrate diets with increased meat consumption have also been promoted for body weight reduction and the prevention and treatment of diabetes and coronary heart disease. These diets have been shown to be effective in inducing weight loss, reducing insulin resistance, lowering blood fats known as triglycerides and raising high-density lipoprotein cholesterol (HDL-C, or "good" cholesterol) levels, but have tended to increase low-density lipoprotein cholesterol (LDL-C, or "bad" cholesterol) levels. "This lack of a benefit for LDL-C control is a major disadvantage in using this dietary strategy in those already at increased risk of coronary heart disease," the authors write.
David J.A. Jenkins, M.D., of St. Michael's Hospital and the University of Toronto, Ontario, Canada, and colleagues tested the effects of a low-carbohydrate diet high in vegetable proteins from gluten, soy, nuts, fruits, vegetables, cereals and vegetable oils among overweight men and women with high LDL cholesterol levels. A total of 25 participants were randomly assigned to consume this diet—the "Eco-Atkins" diet—for four weeks, while an additional 25 participants ate a control diet that was high-carbohydrate, lacto-ovo vegetarian and based on low-fat dairy and whole grain products. Study food was provided to participants at 60 percent of their estimated calorie requirements.
Of the 47 participants who began the study, 44 (22 in each group) completed the four-week period. Weight loss was similar—about 4 kilograms or 8.8 pounds—in both groups. However, reductions in LDL-C levels and improvements in the ratios between total cholesterol and HDL-C were greater for the low-carbohydrate diet compared with the high-carbohydrate diet. The low-carbohydrate diet also appeared to produce beneficial changes in levels and ratios of apolipoproteins, proteins that bind to fats. In addition, small but significantly greater reductions were seen in both systolic (top number) and diastolic (bottom number) blood pressure for the low-carbohydrate vs. the high-carbohydrate group.
Pending answers to important questions, including whether further reducing carbohydrate intake would produce additional benefits, "a plant-based low-carbohydrate diet high in vegetable proteins and oils may be an effective option in treating those with dyslipidemia for whom both weight loss and lower LDL-C concentrations are treatment goals," the authors conclude.
(Arch Intern Med. 2009;169:1046-1054. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: This study was supported by Solae, LLC, Loblaw Companies Limited and the Canadian Research Chair Program of the Federal Government of Canada. Co-author Ms. Wong is a recipient of a Canadian Institutes of Health Research Doctoral Research Award. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.
Editorial: Additional Research Needed Before Recommending "Eco-Atkins" Diet
"High-protein, low-carbohydrate diets are advocated by many, predominantly commercial, weight loss programs," write Katherine R. Tuttle, M.D., and Joan E. Milton, M.S., R.D., C.D., of the Providence Medical Research Center at Sacred Heart Medical Center and the University of Washington School of Medicine, Spokane, Wash., in an accompanying editorial.
"Most of these diets have been promoted within popular culture and until recently have been subjected to little scientific scrutiny. Substantial concern has been raised about the potential for adverse effects. Meat is commonly consumed as a major source of dietary protein. However, meat derived from animal muscle also typically contains large amounts of saturated fat and cholesterol."
"The article by Jenkins et al provides insight into debatably more effective and possibly safer tactics for designing higher-protein diets for weight loss and cardiovascular risk reduction. However, it is premature to recommend the 'Eco-Atkins' diet as a weight loss diet of choice without confirmation of its efficacy in larger studies of more diverse and higher-risk individuals. Long-term studies are also essential to ascertain both sustainability and safety."
(Arch Intern Med. 2009;169:1027. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: Please see the article for additional information, including author contributions and affiliations, financial disclosures, funding and support, etc.