Safflower oil is common cooking oil, while conjugated linoleic acid (CLA) is a compound naturally found in some meat and dairy products, which has been associated with weight loss in previous studies.
Both are composed primarily of polyunsaturated fatty acids, which are considered "good fats", which, when consumed in proper quantities, could lead to a variety of health benefits.
By comparing the two oils, the researchers found that16 weeks of supplementation with safflower oil reduced fat in the trunk area, lowered blood sugar, and increased muscle tissue in the women participants.
On the other hand, conjugated linoleic acid supplementation for the same length of time reduced total body fat, and lowered the women's body mass index (BMI).
The women, who participated in the study, took one type of oil for 16 weeks, followed by the other oil for an equal amount of time.
The participants were instructed not to change their diets or exercise patterns over the course of the study, so the research would measure the effects of only the supplementation.
"Making this subtle change in the intake of high-quality dietary fats in an effort to alter body composition is both achievable and affordable to postmenopausal women in the United States who are managing the difficult combination of obesity and diabetes," said Martha Belury, professor of human nutrition at Ohio State University and senior author of the study.
One of the most surprising finding was that, in 16 weeks, these women could lose between about two pounds and four pounds of trunk fat simply by taking safflower oil supplements.
The study showed that CLA supplementation significantly decreased body mass index and total body fat over both diet periods.
"I never would have imagined such a finding. This study is the first to show that such a modest amount of a linoleic acid-rich oil may have a profound effect on body composition in women," said Belury.
The dose of either oil taken each day was approximately 1 2/3 teaspoons.
Postmenopausal women tend to lose muscle at the same time that body fat accumulates toward their middle.
Thus, the research shows how dietary oils can complement lifestyle and medication in helping older diabetic women manage their health, said Belury.
The research has been published online, and is scheduled for later print publication, in the American Journal of Clinical Nutrition.