Athletes whose diet consists of a relatively high proportion of nuts, avocado and olive oil burn more energy after training than athletes who get most of their fats from dairy, meat, and palm oil. Researchers at the University of Texas in Galveston discovered this after doing an experiment with 19 healthy adults aged between 18 and 35.
The food industry would like us to consume large amounts of palmitic acid, a saturated fatty acid. It's the most important fatty acid in processed meat and dairy products, and also in palm and coconut oil. These oil types are common in ready-made foods like pizzas, cookies and sauces.
The traditional human diet contained high amounts of the mono-unsaturated fatty acid oleic acid, found in nuts, seeds and olives. It may well be the case that these foods were the most important sources of fat in the Stone Age. Only land animals in captivity develop thick layers of fat.
Nutritionists think that a high intake of saturated fatty acids leads to a reduction in the metabolic rate. Enzymes that convert fatty acids into energy have more difficulties with palmitic acid molecules [uppermost structural formula] than with oleic acid molecules [lower structural formula].
The researchers wondered whether the fatty acid composition in the diet influences excess post-exercise oxygen consumption [EPOC]. Oxygen consumption increases as a result of the repair and recovery processes that take place after exertion. The higher the EPOC, the more calories you burn and the more thorough the repair processes are. After intensive exercise in particular, like strength training and interval training, the EPOC is high.
The researchers gave half of their subjects a diet for 28 days in which 42.1 percent of the fats consisted of palmitic acid [PA]. The other half were given a diet in which 78.4 percent of the fats consisted of oleic acid [OA].
At the end of the 28 days the subjects had to cycle for 80 minutes at 60 percent of their maximal oxygen uptake. The researchers suspected that this level of exertion would raise the EPOC, but that untrained individuals would manage to complete it. The graph above shows that the EPOC in the OA group was higher than in the PA group.
In the time span from 60-270 minutes after the workout, the OA group's oxygen consumption had increased by 9.7 percent, but the PA group's consumption remained the same. In the first 60 minutes after the workout the OA group consumed more oxygen than the PA group, but the difference was not statistically significant.
The difference they observed was small, the researchers admit, but nevertheless the EPOC after a good hour's cycling at a reasonable pace is not high either. What would have happened if the researchers had got their subjects to do weight training?
And while we're asking questions: would strength athletes see more progression if they intensified their post-training repair processes by altering the fatty acid composition of their diet?
Metabolism. 2006 Sep;55(9):1215-21.