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11.11.2010


Your body burns unsaturated fat better after exercise

The body's energy expenditure remains high for hours after exercising, a phenomenon that goes by the acronym EPOC. In 2003 nutritionists at the University of Wisconsin discovered that the body prefers to burn the monounsaturated fatty acids in olive oil for EPOC instead of the saturated fatty acids found in meat and greasy snacks. Yet another reason to moderate your intake of saturated fatty acids, and, where possible, to replace them with monounsaturated ones.

Your body burns unsaturated fat better after exercise
If you are inactive your body will choose to burn monounsaturated fatty acids over saturated fatty acids. But what if you've exercised earlier in the day? Replenishing the glycogen reserves, and of course muscle tissue recovery, both cost the body energy. After strength training the body usually gets this energy from fat.

Because they wanted to know what kind of fat the body prefers after exercise, the researchers set up an experiment with 38 women. The subjects were put on pre-breakfast programmes: no activity [rest], two hours of cycling at 25 percent of their VO2max [light], 30-45 minutes at 65 percent of their VO2max [moderate] or 3 times 10 minutes at 85 percent of their VO2max [heavy].

After the exercise the women were given breakfast [time = 0], in which the researchers had marked the palmitate [a saturated fatty acid found in fat meat and ready-prepared products] and the oleate [a monounsaturated fatty acid found in olive oil]. The markers enabled them to measure the amount of the different fats the women had burned, as they showed up in their urine and the carbon dioxide they exhaled.

The women were given lunch in the middle of the day [L] and an early supper [D], but none of the fatty acids were marked in these.

When the researchers looked at how many kcal the women burned throughout the whole day, they noticed that exercise led to a boost in energy expenditure over the whole day and that that energy came mainly from fats.


Your body burns unsaturated fat better after exercise


The women burned hardly any more palmitate after exercise [figure immediately below], but did burn more oleate [second figure below].


Your body burns unsaturated fat better after exercise


Your body burns unsaturated fat better after exercise


After moderate exercise the test subjects burned 17 percent of the palmitate they had consumed. When the subjects had not exercised at all they still burned 12 percent. After the same moderate exercise the subjects burned 54 percent of the labelled oleate. Without exercise the amount was 33 percent.

So substituting unsaturated fatty acids for saturated ones makes it easier to maintain your weight. What's more, this may help speed up muscle recovery. A diet with fewer saturated fatty acids and more unsaturated ones raises the EPOC, and therefore may speed up post-exercise muscle recovery.

Source:
Obes Res. 2003 Dec; 11(12): 1509-18.