Definition
Fat metabolism in general refers to the absorption, digestion and processing of fats. We absorb fats through food or build them up from precursors ourselves and use them, for example, to provide energy or to produce important messenger substances in the body. After carbohydrates, fats are the most important suppliers of energy for our body. Depending on the composition of the food, the proportion of carbohydrates, fats and proteins ingested and thus the energy content varies.
Function
Fat metabolism begins with the absorption of fats in the intestine. There the fats are split and transported mainly via the lymphatic system into the blood, where they are bound to proteins and distributed in the body as so-called lipoproteins. Fats are mostly used to store energy so that the body is always able to provide sufficient energy even in times of low food intake.
In addition to the fats ingested through food, fats can also be formed from carbohydrates, which are stored in the body’s fat stores. The hormone insulin is of crucial importance for the balance between fat synthesis and fat breakdown. Insulin couples the carbohydrate supply of food with the fat synthesis in the body and, in the case of a high carbohydrate supply, promotes the synthesis and incorporation of fat.
As soon as the stored fats are needed, they are split into smaller components and are thus available for energy supply. Accordingly, the fat store serves as a reserve and less as a basic supply. In contrast to fat burning, carbohydrate burning provides twice as much energy per time, but the energy from fat burning lasts much longer and fats are available in the body without restriction.
However, fats absorbed through food have many more functions. For example, they are precursors for numerous hormones. So-called steroid hormones, such as the sex hormones testosterone or estrogen, are produced from fats.
Furthermore, the body can produce vitamin D from fats itself with the help of sunlight. Fats are converted to cholesterol, which acts as a precursor for the synthesis of vitamin D. Membranes, which separate cells and cell components in the body from each other, consist of so-called lipid bilayers. These two membrane layers are also composed of fat components.
Fats are not only built into the body as energy stores, but also as building fat, which serves to cushion some organs. The kidneys, for example, are surrounded by building fat so that they are padded when the body moves jerkily. The same applies to the fat storage in the eye socket, which protects the eye all around.