New research from Uppsala University shows that saturated fat builds more fat and less muscle than polyunsaturated fat. This is the first study on humans to show that the fat composition of food not only influences cholesterol levels in the blood and the risk of cardiovascular disease but also determines where the fat will be stored in the body. The findings have recently been published in the American journal Diabetes.
The study involved 39 young adult men and women of normal weight, who ate 750 extra calories per day for seven weeks. The goal was for them to gain three per cent of their starting weight. The project received considerable attention when it started in 2011, partly because the extra calories were ingested in the form of muffins with high fat content, baked in the lab by Fredrik Rosqvist, a doctoral candidate and first author of the study.
One half of the subjects were random to eat surplus calories from polyunsaturated fat (sunflower oil), while the other half got their surplus calories from saturated fat (palm oil). Both diets contained the same amount of sugar, carbohydrates, fat, and protein; the only difference between muffins was the type of fat.
The increase in body fat and the distribution of fat in the body was measured using a magnetic resonance imaging (MRI scans) before and after the weight gain, as was the muscle mass in the body. Gene activity was measured in the abdominal visceral fat before and after the weight gain with the help of a gene chip that studies several thousand genes at a time.
Despite comparable weight gains between the two diet groups, the surplus consumption of saturated fat caused a markedly greater increase in the amount of fat in the liver and abdomen (especially the fat surrounding the internal organs, visceral fat) in comparison with the surplus consumption of polyunsaturated fat. Moreover the total amount of body fat was greater in the saturated fat group, while, o
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