| Abstract: | Fats, as fatty acids (FA), together with carbohydrates, represent a major substrate group for energy production. In contrast to carbohydrates FA are less efficiently used for energy and more easily stored in tissues. A major issue, still not completely solved, concerns the origin of FA in the organism. The two theoretical alternatives are a) endogenous de novo lipogenesis from carbohydrates, and b) supply through the diet. Various pieces of evidence indicate that the first option, while well‐documented in simple biological systems, plays a minimal role in vivo. The exogenous origin therefore represents the preferred, major route of FA supply to the body. This is also supported by the observation that only the enzymes involved in the production of long‐chain polyunsaturated FA from their precursors, and not those involved in the synthesis of the FA that are abundant in the diet, are operating in vivo. Finally, as a consequence of the load of fats in our diets, competition for esterification, and reciprocal replacements, of the unsaturated FA and FA classes, that are most abundantly provided by the diet, take place in plasma lipids. |
