People, who consume a diet high in polyunsaturated fat, develop more muscles and less fat than those who consume saturated fat, according to an Uppsala University study. 

The Swedish researchers said that eating salmon and walnuts rich in polyunsaturated fat helps amass less fat around the waist and internal organs.

This is the first study to determine how different types of fat are stored in different parts of the body.

For the study, the researchers asked 39 young adult men and women of normal weight to consume 750 extra calories a day for seven weeks. Half of the participants were given foods rich in polyunsaturated fat - sunflower oil - while the rest were offered palm oil, rich in saturated fat.

The diet for both groups contained similar amounts of sugar, carbohydrates, fat, and protein. The only difference between both the groups was the nature of fat.

Researchers later measured body fat, distribution of fat and muscle mass using MRI scans. Gene activity was measured in the abdominal fat through a gene chip capable of studying several thousand genes at a time.

The scientists found that both the groups reported similar weight gains. However, the overall body fat was higher in participants that consumed saturated fat/ palm oil. They also had higher fat around the liver and abdomen and developed three times lesser muscles than those who consumed polyunsaturated fats.

The researchers also found that saturated fats activated certain genes in fatty tissue that increased the accumulation of fat in the abdomen and hindered insulin regulation. However, the polyunsaturated fats switched on genes in visceral fat that is responsible for reduced fat storage and improved sugar metabolism in the body.

"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," Ulf Risérus, associate professor at the Department of Public Health and Caring Science and director of the study, said in a press release.

The experts said the finding suggests that people who consume more polyunsaturated fat are less likely to develop heart diseases and metabolic diseases like diabetes.

When fat gets accumulated around internal organs, it leads to type 2 diabetes and cardiovascular disease. Previous studies have showed that consumption of polyunsaturated fat from plants, oils, and nuts decreases the risk of type 2 diabetes.

Saturated fat is found in butter, cake, biscuits, fatty cuts of meat, cheese and cream, while unsaturated fats are present in oily fish, nuts, seeds and olive oil.