The moderate-fat diet, in which half the fat was monounsaturated fat from peanuts and peanut oil, produced a 14 percent reduction in cardiovascular disease risk. The low fat group experienced a nine percent improvement. Both the moderate and low fat diets were controlled so that all participants lost about the same amount of weight -- approximately 2.4 to 2.7 pound a week on average.
Dr. Penny Kris-Etherton, distinguished professor of nutrition, says, "While the low-fat diet successfully reduced risk factors during the weight loss phase of the study, those factors rebounded during the maintenance phase."
The study is in the February issue of the American Journal of Clinical Nutrition in a paper, "Effects of Moderate-Fat (from monounsaturated fat) and Low-fat Weight-loss Diets on the Serum Lipid Profile in Overweight and Obese Men and Women." The authors are Dr. Christine Pelkman, former Penn State postdoctoral researcher who is now at the University at Buffalo; Kris-Etherton; Valerie K. Fishell, former Penn State research assistant; Deborah Maddox, Penn State clinical coordinator; Dr. Thomas A. Pearson, University of Rochester; and Dr. David T. Mauger, associate professor health evaluation sciences, Penn State College of Medicine.
Fifty-three overweight or obese men and women participated in the study. All of the participants had total cholesterol levels elevated above 200 at the start of the dieting.
The participants ate either a low-fat or moderate-fat diet designed to produce weight loss for six weeks and then similar diets designed for maintenance for four weeks. The foods were all provided by the researchers and provided 18 percent of calories from fat in the low-fat diet or 33 percent of calories from fat in the moderate fat diet.
Over the course of the study, the low-fat diet group experienced a 12 percent decrease in HDL ("good") cholesterol but the moderate-fat diet group had no change. This indicates that a moderate-fat diet blunts the decrease in HDL ("good") cholesterol during weight loss.
In addition, after falling during the weight loss phase, triglycerides rose significantly during the maintenance phase for those on the low fat diet but not for those on the moderate fat diet. Elevated triglycerides are a cardiovascular risk factor.
The authors write, "The findings of this current study are significant because they demonstrate that markedly lowering total fat intakes may have adverse consequences on reductions in the risk of CVD, even in response to weight loss."