Penny Kris-Etherton of Pennsylvania State University and colleagues said the study involved 121 participants at risk for metabolic syndrome, who received a daily smoothie containing 40 grams -- 1.42 ounces -- of one of five oils as part of a weight maintenance, heart-healthy, 2000-calorie per day diet.
Members of the group had five risk factors characterized by increased belly fat; low high-density lipoprotein, the "good" cholesterol and above average blood sugar, blood pressure and triglycerides that increase the risk of heart disease, stroke and type 2 diabetes.
The study found those who consumed canola or high-oleic canola oils on a daily basis for four weeks lowered their belly fat by 1.6 percent compared to those who consumed a flax/safflower oil blend.
Abdominal fat was unchanged by the other two oils, which included a corn/safflower oil blend and high-oleic canola oil enriched with an algal source of the omega-3 DHA. Both the flax/safflower and corn/safflower oil blends were low in monounsaturated fat, the researchers said.
"It is evident that further studies are needed to determine the mechanisms that account for belly fat loss on a diet high in monounsaturated fatty acids," Kris-Etherton said in a statement.
The findings were presented at the American Heart Association Scientific Sessions in New Orleans.