The study group consisted of 53 overweight or obese men and women between the ages of 20 and 67 who were assigned randomly to either the low- or moderate-fat diet. All meals were provided, and weight loss was kept constant at an average of 2.4 to 2.7 pounds a week. Both diets met current saturated fat and cholesterol recommendations.
Carbohydrates replaced the calories from saturated fats in the low-fat diet, while monounsaturated fats replaced saturated fats in the moderate-fat diet. Chemical analysis of the diets validated the composition of the two diets.
During the weight-loss period, both groups lowered their total and LDL cholesterol, but the low-fat group also experienced a 12 percent drop in HDL cholesterol. Triglycerides dropped in both groups, as well. However, during the weight-maintenance phase, there was a reversal of the weight-loss induced drop in triglycerides and a reduction in HDL cholesterol compared to baseline in the low-fat group, but not in the moderate-fat group.
"These results show that although weight loss does improve the lipid profile, a moderate-fat, weight-loss diet reduces risk more than a low-fat, weight-loss diet, so dieters don't need to cut out all the fat to improve their risk profile," Pelkman said. "Monounsaturated fats can be a healthy part of a weight-loss diet."