Conventional diet wisdom says to stay far, far away from fat. So does science, with some research showing a high-fat diet can spike cholesterol levels and heart disease risk. While that’s not not true, it’s misguided to advise against eating fat altogether. There are, in fact, good and bad fats — and what better way to make that point than by feeding a bunch of people muffins?

That was the premise of a Swedish study recently published in the Journal of the American Heart Association. Granted, the purpose of the study was for 39 adults to achieve a three percent weight gain, but the three muffins added to their daily diet were specifically made from either unsaturated sunflower oil (good fat) or saturated palm oil (bad fat). A muffin was added or subtracted depending how much weight a participant gained. Otherwise, they kept with their regular diet and fitness routine.

Researchers found a nine percent difference in bad, LDL cholesterol levels, as well as a nearly 18 percent difference in good, HDL cholesterol levels, among those eating muffins made from unsaturated versus saturated fat. The numbers tipped in favor of the unsaturated group, increasing positive indicators for cardiovascular health. No, the carbohydrates and sugar were not magically missing from the muffins, but researchers only found those made from saturated fat to be problematic.

Unsaturated fat is formally known as polyunsaturated fat. According to the American Heart Association (AHA), “oils rich in polyunsaturated fats also provide essential fats that your body needs but can’t produce itself — such as omega-6 and omega-3 fatty acids.” In addition to sunflower oil, soybean and corn oil are rich in polyunsaturated fats. Beyond oil, fatty fish, such as salmon and mackerel, nuts, seeds, and tofu are rich in this healthy fat, too.

"Even in early adulthood, it is important to avoid high-calorie foods and weight gain, but also it is important to consume sufficient amounts of polyunsaturated fats from non-hydrogenated vegetable oils," Dr. Ulf Risérus, lead study author and associate professor of Clinical Nutrition and Metabolism at Uppsala University, in Uppsala, Sweden, said in a press release. “The lowering of the cholesterol/HDL cholesterol ratio by polyunsaturated fat is of special interest because recent large studies have shown this ratio seems to predict heart disease risk even better than LDL levels alone."

Since it was intended for participants to gain weight, Risérus added that these effects were noticeable in less than two months, which could implicate why “individuals gain weight due to excess calorie intake from both sugars and fats and lack of physical activity.” Risérus also believes the effects of a high-saturated fat diet can be reversed.

Source: Risérus U, Iggman D, Rosqvist F, Larsson A , Ärnlöv J, et al. Journal of the American Heart Association. 2014.