In this article, we first report the importance of lipid metabolism in the fulfilling of energy requirements through nutritional states and describe the structures implied in this pathway. We thereafter present in detail the catabolic pathway allowing energy to be produced from fatty acid beta-oxidation, and we point out the essential role of the chemical structure of these fatty acids. Lastly, we focus on the fact that this pathway is regulated in many differents ways. The different steps of the catabolism may be submitted to biochemical or gene regulation control (such as that mediated by carnitine palmitoyltransferase I or fatty acid regulation of gene transcription via PPAR).