Factors affecting fat oxidation in exercise

Increasing fat oxidation rates during exercise may be beneficial for the athletic population. At rest, ingestion of Green Tea Extract (GTE) has been found to augment fat oxidation, but there are limited data on the effects during exercise. This thesis systematically investigated the effects of GTE ingestion on exercise metabolism in physically active males. We set out to determine if longer-term feeding of GTE could increase fat oxidation rates during a steady state exercise bout to a greater degree than an acute dose. However, irrespective of the length of ingestion no measureable change in substrate metabolism was found. Due to the large individual differences in fat oxidation at a given absolute and relative exercise intensity, we investigated the effects of acute GTE ingestion during a graded exercise test. Again, no change in fat metabolism was found over a wide range of exercise intensities. Finally, we collected fat oxidation data from a large cohort of athletes. From these data we set new criteria to define individuals as either a fat or carbohydrate metabolic type. Although it is still not known fully what determines metabolic type, the use of a nutritional intervention may be more effective in one type over the other.