ABSTRACT
From a human point of view fat or adipose tissue is nowadays often considered as superfluous and undesired, especially considering the current “emaciated” beauty ideal of the Western world. This could ultimately lead to the provocative question: “Do we really need adipose tissue for normal life?” (see also the introduction to Chapter 3 of this volume). The answer to this question can be approached from different angles. From an evolu tionary perspective it was very important especially for homeothermic animals (mammals and birds) to develop the ability to store relatively large amounts of energy. Homeothermic animals are able to keep their body temperature at a constant high level which enables them to be active in cold environments, i.e., very high and low latitudes, during the winter and also at night, thus giving them an advantage over endothermic animals like insects or reptiles. However, this implies a high, continuous energy expenditure for thermogenesis. As food, i.e., an exogenous energy supply is not continuously available, a significant energy reservoir is essential for survival in times of food scarcity. From a clinical point of view, loss of adipose tissue as encountered in syndromes of lipodystrophy or lipoatrophy is associated with severe metabolic complications like diabetes, hypermetabolism, and organomegaly of several organs including the liver (for review see ref. 1). Interestingly, recently developed transgenic mice with virtually no white fat displayed very similar symptoms.2 Together this implies that adipose tissue is indeed important for normal physiological functions and metabolism and is not only an energy reservoir for emergency situations.
