SOURCES: Ulf Riserus, M.D., Ph.D., associate professor, clinical nutrition and metabolism, Uppsala University, Sweden; Samantha Heller, M.S., R.D., senior clinical nutritionist, New York University Medical Center, New York City; Oct. 15, 2014, Journal of the American Heart Association, online
THURSDAY, Oct. 16, 2014 (HealthDay News) -- Muffins -- and other fatty foods -- can definitely put on the pounds, but those made with polyunsaturated oil may be safer for your heart than if they're made with saturated fats like butter, a small study suggests.
That's because soybean oil, corn oil, sunflower oil and other polyunsaturated fats won't increase cholesterol like butter or palm oil, the researchers found.
Thirty-nine healthy young adults in Sweden were asked to add four muffins a day to their diet so that researchers could evaluate the effects of different cooking fats.
All of the volunteers gained weight, but those whose muffins were made with unsaturated sunflower oil had better cholesterol levels after seven weeks than the group that ate muffins baked with butter or palm oil, another saturated fat, the study found. High cholesterol is linked with an increased risk of heart disease.
"Even modest weight gain of less than 4 pounds may have adverse effects, but having sufficient amounts of polyunsaturated fats and less saturated fats may prevent some of the unwanted consequences with weight gain," said lead researcher Dr. Ulf Riserus, an associate professor of clinical nutrition and metabolism at Uppsala University in Sweden.
However, no one can eat a steady diet of sugary muffins and get off scot-free. Both groups showed increased insulin resistance, a warning sign of adult-onset diabetes, Riserus said.
The researchers aimed for participants, whose average age was 27, to gain about 3 percent of their body weight. Muffins were added or subtracted to keep weight gain within that range, while the volunteers continued their normal diet and physical activity.
Over seven weeks, people in both groups gained about 2.2 percent of their body weight. However, those whose muffins contained unsaturated fat had lower levels of bad cholesterol (low-density lipoproteins, or LDL). They also had higher levels of good cholesterol (high-density lipoproteins, or HDL) than those whose muffins were made with saturated fat, the researchers found.
LDL levels between the groups differed by 9 percent. In terms of overall cholesterol/HDL cholesterol ratio, the difference was as much as 18 percent, the researchers said. This is important because this ratio seems to predict heart disease risk even better than LDL levels alone, Riserus said.
A diet high in polyunsaturated fats rather than saturated fats lowers cholesterol, Riserus said. Polyunsaturated fats include safflower oil, corn oil, soybean oil and canola oil, according to the U.S. Centers for Disease Control and Prevention.
"As more than half of the Western populations consume an excessive amount of calories and gain weight over time, these results are clearly relevant and suggest that regular intake of vegetable oils and nuts are of some benefit also in people who are gaining weight," Riserus said.
He added that the effects of a diet high in saturated fat may be reversible. His team hopes to prove this theory with results from a new study that follows people for a month after weight gain.
The new report, funded by the Swedish Research Council, was published Oct. 15 online in the Journal of the American Heart Association.
"This small study highlights what we already know about saturated fats, and how quickly a relatively small amount of saturated fat can cause health disturbances," said Samantha Heller, a senior clinical nutritionist at New York University Medical Center in New York City.
Saturated fat is associated with an increased risk of arteriosclerosis, diabetes and nonalcoholic fatty liver disease, and may increase fat storage in the abdomen, Heller said.
How can you distinguish between saturated and polyunsaturated fats? "The simplest way to identify a saturated fat is either by how it looks or knowing the source," she said.
Fats that are solid at room temperature are saturated and are primarily found in animal foods such as red and processed meats, cheese, butter, lard and ice cream. "In the plant world, palm and coconut oils are saturated fats," Heller said.
Fats that are liquid at room temperature, like grape-seed, walnut, canola and peanut oils, are unsaturated and come from plants, Heller said. "Foods such as avocados and nuts contain unsaturated fats that confer many health benefits," she added.
Eating more plant foods -- think black beans, lentils, quinoa, edamame, spinach, broccoli, apples and brown rice -- can help limit your saturated fat consumption and increase intake of heart-healthy vitamins, minerals, antioxidants and fiber, Heller said.
For more about saturated fats, visit the American Heart Association.