Fat metabolism is often mistaken for body fat reduction. Fat metabolism can be promoted in many ways by substances like L-carnitine, caffeine, green tea. Increased fat metabolism (fatty acid oxidation) in muscle cells is especially important for endurance athletes whereas others want to reduce their fat deposits. Fatty acid oxidation mainly occurs in muscle cells and in metabolically active visceral fat which surrounds many organs. In order to reduce fat deposits, lipolysis (release of fatty acids from adipose cells) has to be boosted by increased physical activity. This ensures that the released fatty acids are metabolised and not stored again.