Pre-exercise fat ingestion (i.e., long chain triacylglycerol ingestion 1 to 4 h before exercise), medium-chain triacylglycerols, fish oil, and conjugated linoleic acid have been suggested to alter metabolism to achieve weight loss, alter lipid profiles, or improve performance. However, studies have demonstrated that ingestion of meals with long-chain triacylglycerols before exercise has little or no effect on metabolism and does not alter subsequent exercise performance. Also, medium-chain triacylglycerol supplementation before or during exercise has not been shown to be ergogenic, although this could be related to the small amounts of medium-chain triacylglycerol that can be ingested before gastrointestinal discomfort occurs. Fish oil may improve red blood cell deformability, but these effects are likely to be small and do not seem to influence maximum oxygen delivery or exercise performance. Conjugated linoleic acid has been implicated in weight loss, but based on the results of human studies it must be concluded that the effects of conjugated linoleic acid on body weight loss are far less clear than those observed in animal studies. Most studies have not found any evidence for a beneficial effect of conjugated linoleic acid.