During exercise, both fat and carbohydrate are metabolized to produce energy. At lower intensities and rest, fat is the predominate substrate that is metabolized. As intensity increases, carbohydrate metabolism increases and fat metabolism decreases. Incremental exercise tests have been developed on both a cycle ergometer and treadmill to measure the maximal fat oxidation (MFO) and at what intensity MFO occurs (FATMAX). It has been shown that there is large individual variation in MFO and FATMAX, and that individuals may have a unique FATMAX curve. Increasing an athlete’s fat oxidation may be beneficial as it could preserve the limited amount of muscle and liver glycogen, which could then delay fatigue. Several nutritional supplements thought to increase fat oxidation have been studied, such as; green tea, New Zealand blackcurrants, caffeine, and Omega-3. In addition to supplementation, training strategies to decrease muscle and liver glycogen availability prior to exercise have been shown to increase fat oxidation during exercise. It is important to note that an increase in fat oxidation during exercise has not been associated with improved performance.
Commission on Dietetic Registration