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Page 4 of 5
Thermic Effect For Increased Fat Burning
After collecting the data, it was noted that none of the EFAs significantly affected the relative fat-burning for calories, as the same ratio of fat to carbohydrate was used to produce calories in all subjects at baseline as after receiving the test meal. However, there was a significant difference in the rate of total calorie burning in subjects after consuming the OA (olive oil) test breakfast. The olive oil-containing breakfast increased energy expenditure, resulting in a greater total calorie burning, and thus an increase in total fat burning. The subjects remained in a contained observation area, at rest. The increase in energy expenditure was not related to an increase in activity but appears to be related to the thermic effect of the olive oil (thermic effect describes the increase in body temperature after eating). Though it has not been measured in humans, rat studies have shown that olive oil consumption increases uncoupling protein content (uncoupling proteins cause calorie-burning reactions to spin-off the energy as heat instead of supplying cellular energy or ATP).13 It is possible that a diet rich in olive oil may increase the activity of uncoupling proteins in humans as well.
Other studies have shown that OA is preferentially burned, as opposed to being stored as body fat, and the results of this experiment would support those findings.14,15 However, an interesting finding is that the increased fat-burning does not appear to be limited just to OA, but rather may reflect an increase in total fat and calorie burning by increasing the metabolic rate. To state it more clearly, other fats stored in body fat may be burned more rapidly as well as OA. Though the results did not reach statistical significance, the test subjects experienced an increase in fat-burning and slight decrease in carbohydrate-burning after the OA meal.12 Endurance athletes in particular may wish to investigate the use of olive oil as a dietary fat source to promote fat-burning during marathon-like events.
It is important to note that this experiment was short, following the subjects for just a few hours; also, the calorie-burning effect, though statistically significant, was fairly small. It was interesting to note that sunflower oil (LA, omega-6) was very close to showing significant metabolism-boosting in comparison to flaxseed oil (ALA, omega-3).12 This contrasts somewhat with other studies that have shown that fish oils (omega-3 fatty acids, DHA & EPA) increase weight loss, as ALA is the precursor to DHA and EPA in humans.16 It may be that the long-term effect of specific fatty acids, such as DHA and EPA, are too slow to show a near-immediate effect. Given that there is evidence of several different types of unsaturated fatty acids affecting the metabolism and fat storage, it is suggestive that the best health effects are seen when a person consumes a variety of different fat sources in a macronutrient-balanced diet; even sacrificing simple sugars and other carbohydrates for EFAs when weight loss is the priority.
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Research and Review 
