The Diet-Heart Hypothesis: A Critique by Sylvan Lee Weinberg, MD, MACC
The low-fat "diet heart hypothesis" has been controversial for nearly 100 years. The low-fat, high-carbohydrate diet, promulgated vigorously by the National Cholesterol Education Program, National Institutes of Health, and American Heart Association since the Lipid Research Clinics-Primary Prevention Program in 1984, and earlier by the U.S. Department of Agriculture food pyramid, may well have played an unintended role in the current epidemics of obesity, lipid abnormalities, type II diabetes, and metabolic syndromes. This diet can no longer be defended by appeal to the authority of prestigious medical organizations or by rejecting clinical experience and a growing medical literature suggesting that the much-maligned low-carbohydrate, high-protein diet may have a salutary effect on the epidemics in question.
(J Am Coll Cardiol 2004;43:731-3) © 2004 by the American College of Cardiology Foundation
Weight and Metabolic Outcomes after 2 Years on a Low CarbohydrateVersus Low-Fat Diet - A Randomized Trail
Annals of Internal Medicine - Volume 153, pages 147-157.
G.D. Foster, H.R. Wyatt, J.O. Hill, A.P. Makris, D.L. Rosenbaum, C. Brill, R.I. Stein, B.S. Mohammed, B. Miller, D.J. Rader, B. Zemel, T.A. Wadden, T. Tenhave, C.W. Newcomb, and S. Klein.
Low-carbohydrate diets are popular among persons who want to lose weight. Previous studies suggest that early weight loss occurs with low-carb diets rather than low-fat diets although after 1 year, the results are mixed and any weight loss tends to be small. Previous studies comparing these 2 types of diets have not included a very wide area of behavioral support programs to help patients change other aspects of their lifestyle. It is possible that people could lose more weight if diet is combined with other types of support.
The study included 307 persons with a body mass index (BMI) of 30 to 40 kg/m2 and each person was assigned to either a low-carbohydrate or a low-fat diet. The low-carbohydrate group were told to eat no more than 20 grams of carbohydrate per day for 3 months and then increase by 5 grams per day each week until they achieved their desired weight. The low-fat diet group received instructions to decrease calorie intake to 1200 to 1800 kcal per day with no more than 30% of calories from fat. All patients also participated in an education program on changing physical activity and other lifestyle factors. The participants met every week for 20 weeks, then every other week for 20 weeks, then monthly for the rest of the 2-year study.
After 2 years, patients lost an average of 7 kg or 7% of body weight, and no differences between the 2 groups were found. The low-carbohydrate group had some more favourable changes in risk factors for heart disease compared with the low-fat diet group.
The study did not include persons with cholesterol problems or diabetes, so the results might
not apply to patients with these conditions. Many withdrew from the study by 2 years.
The researchers concluded that after 2 years, successful weight loss can be achieved with either type of diet combined with a behavioral program and a low-carbohydrate diet may modestly improve some, but not all, risk factors for heart disease. It is unknown whether these improvements will influence the future development of heart disease.