Strategies to Enhance Fat Utilisation During Exercise

May 20, 1998Sports medicine (Auckland, N.Z.)

Ways to increase fat use for energy during exercise

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Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

Endurance-trained individuals may not experience improved exercise performance from a high fat diet over 7 to 10 days.

Fatty acid oxidation is limited during intense exercise, making carbohydrates the primary fuel for energy.
Caffeine ingestion may enhance endurance capacity in some individuals.
L-carnitine supplementation does not affect fatty acid oxidation or muscle glycogen utilization.
Small amounts of medium-chain triglyceride (MCT) do not significantly influence fat metabolism or exercise performance.
Adapting to a high fat, low carbohydrate diet does not consistently improve performance or alter muscle glycogen utilization during moderate intensity exercise.
Current evidence does not support the use of MCTs or 'fat-adapting' for enhancing athletic performance in endurance sports.

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Compared with the limited capacity of the human body to store carbohydrate (CHO), endogenous fat depots are large and represent a vast source of fuel for exercise. However, fatty acid (FA) oxidation is limited, especially during intense exercise, and CHO remains the major fuel for oxidative metabolism. In the search for strategies to improve athletic performance, recent interest has focused on several nutritional procedures which may theoretically promote FA oxidation, attenuate the rate of muscle glycogen depletion and improve exercise capacity. In some individuals the ingestion of caffeine improves endurance capacity, but L-carnitine supplementation has no effect on either rates of FA oxidation, muscle glycogen utilisation or performance. Likewise, the ingestion of small amounts of medium-chain triglyceride (MCT) has no major effect on either fat metabolism or exercise performance. On the other hand, in endurance-trained individuals, substrate utilisation during submaximal [60% of peak oxygen uptake (VO2peak)] exercise can be altered substantially by the ingestion of a high fat (60 to 70% of energy intake), low CHO (15 to 20% of energy intake) diet for 7 to 10 days. Adaptation to such a diet, however, does not appear to alter the rate of working muscle glycogen utilisation during prolonged, moderate intensity exercise, nor consistently improve performance. At present, there is insufficient scientific evidence to recommend that athletes either ingest fat, in the form of MCTs, during exercise, or "fat-adapt" in the weeks prior to a major endurance event to improve athletic performance.

Strategies to Enhance Fat Utilisation During Exercise

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