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07.11.2014

Weight gain? The kind of fat in your diet helps determine how much muscle mass you build up

If you gain weight, the kind of fat in your diet partly determines the amount of fat and the amount of muscle in your newfound kilograms. The unsaturated fatty acids in sunflower oil stimulate the growth of muscle; the saturated fatty acids in palm oil – found in many processed foods – lead to an increase the amount of fat. Researchers at the University of Uppsala in Sweden report on this in Diabetes.

Study
If you fatten lab animals, the type of fat you use makes a difference. If you use vegetable oil, which contains lots of unsaturated fatty acids, the animals build up relatively more muscle than if you use products that contain large amounts of saturated fatty acids. The Swedish researchers were curious to know whether these results would also apply to humans, so they performed an experiment with 39 healthy subjects aged between 20 and 38.

The researchers gave their subjects 3 muffins every day for 7 weeks on top of their ordinary food. The muffins provided a total of 750 kcal – of which half were derived from fat.

Half of the subjects were given muffins prepared with sunflower oil, a source of the polyunsaturated fatty acid linoleic acid. The other half were given muffins made with palm oil, a source of the saturated fatty acid palmitic acid.

Palmitic Acid	Linoleic Acid

The subjects did no sports and took no supplements either.

Results
At the end of the 7 weeks, the subjects in both groups had gained just over 1.5 kg in weight. But those who had been given the unsaturated fatty acid [PUFA] had gained three times more muscle mass than the subjects in the other group [SFA].

The type of fatty acid also had an effect on where the fat layers were deposited. The subjects who had eaten the palm-oil muffins accumulated relatively more fat in the abdominal area than those who had eaten sunflower-oil muffins. Abdominal or visceral fat is less healthy than subcutaneous fat, and increases the chance of a number of diseases including type-2 diabetes and some forms of cancer.

Conclusion
"Despite comparable weight gain after 49 days, this double-blind trial showed that overeating energy from polyunsaturated fatty acids prevented deposition of l visceral and total fat compared with saturated fatty acids", the researchers write.

"Further, the inhibitory effect of polyunsaturated fatty acids on ectopic fat was accompanied by an augmented increase in lean tissue and less total body fat deposition compared with saturated fatty acids. Thus, the type of fat in the diet seems to be a novel and important determinant of liver fat accumulation, fat distribution, and body composition during moderate weight gain."

Source:
Diabetes. 2014 Jul;63(7):2356-68.

More:
Six weeks of fish oil: lose a pound of fat and gain a pound of lean body mass 12.11.2010