Eating saturated fat leads to the accumulation of more visceral fat and less muscle mass than eating polyunsaturated fat, according to new research published in the journal Diabetes. Visceral fat, a dangerous type of abdominal fat that wraps itself around the internal organs, has been linked to metabolic disturbances such as Type 2 diabetes.
Saturated fat is known to raise blood cholesterol levels, increasing the risk of heart disease and stroke. This type of fat is found mostly in animal foods, including meat and dairy products, as well as in many baked goods and fried foods. Polyunsaturated fats, on the other hand, can help reduce blood cholesterol levels and the risk of heart disease. Food sources of polyunsaturated fats include vegetable oils, walnuts and sunflower seeds, and fatty fish such as salmon, mackerel, herring, and trout.
To determine the effects of dietary fat composition on fat storage in the body, researchers at Uppsala University in Sweden looked at 39 young adults who were randomly assigned to eat 750 extra calories per day from high-fat muffins made with either saturated fat (palm oil) or polyunsaturated fat (sunflower oil). Aside from the type of fat in the muffins, all other aspects of the diet — including the sugar, carbohydrate, fat, and protein content — were the same. The participants were given a magnetic resonance imaging (MRI) scan at the start of the study to determine their fat and muscle mass, and also had the gene activity measured in their abdominal visceral fat with the help of a gene chip. The volunteers then ate the muffins daily for seven weeks with the goal of gaining 3% of their starting weight.
At the end of the study period, the volunteers again underwent an MRI scan and had their gene activity measured. The researchers found that, in spite of comparable weight gains between the two groups, those consuming muffins made with saturated fat gained a significantly larger amount of fat in their livers and abdomens than those eating the muffins made with polyunsaturated fat. The increase in muscle mass was also three times less for those consuming the saturated fat. Additionally, it was found that overconsumption of saturated fat activated certain genes in fatty tissue that interfere with insulin regulation and increase the storage of fat in the abdomen.
“Liver fat and visceral fat seem to contribute to a number of disturbances in metabolism. These findings can therefore be important for individuals with metabolic diseases such as diabetes. If the results regarding increased muscle mass following consumption of polyunsaturated fat can be confirmed in our coming studies, it will potentially be interesting for many elderly people, for whom maintaining muscle mass is of great importance in preventing morbidity,” noted study director Ulf Risérus, MMed, PhD.
For more information, read the article “Abdominal fat accumulation prevented by unsaturated fat” or see the study’s abstract in the journal Diabetes. And to learn more about visceral fat, see this three-part series by registered dietitian and certified diabetes educator Amy Campbell.