The role of thermogenesis in the regulation of energy balance

Abstract

Our knowledge of mammalian energetics has improved considerably during the last decade. Some twelve years ago energetics, which was a low priority research area (except perhaps for the agricultural nutritionists), started to revive with the publication of major contributions emphasizing the role of thermogenesis in the regulation of energy balance. Trayhum et al. (1979) observed that obesity in genetically obese mice was associated with a reduced energy expenditure for thermoregulatory thermogenesis. Meanwhile, Rothwell and Stock (1979) published results suggesting that the ability of young leanrats to resist obesity when made hyperphagic by palatable food was due to an increase in a facultative form of thermogenesis. Brown adipose tissue, which was recognized in the meantime as the main site of nonshivering thermogenesis in cold-adapted, cold-exposed rats (Foster and Frydman 1979), was also proposed as the major thermogenic effector in diet-induced thermogenesis. These studies attracted several researchers interested in understanding the etiology of obesity, an energy balance disorder that tends to be too often seen as merely the result of overfeeding. As a consequence, a tremendous amount of literature has emerged from a wide spectrum of disciplines. Although this literature supports the role of thermogenesis in energy balance of experimental animals, it does not provide all the mechanistic bases underlying this action. Besides, the role of thermogenesis in energy balance in man remains to be more firmly established. The present issue of the Canadian Journal of Physiology and Pharmacology contains a series of articles on the role of thermogenesis in energy balance. The following topics are reviewed: the role of thermogenesis in the regulation of energy balance in relation to obesity; the regulation of energy metabolism in diabetes; the role of brown adipose tissue in diet-induced thermogenesis; the role of exercise training in energy balance; and the role of thermogenesis in the energetics of pregnancy and lactation. These articles summarize the current views of some Canadian researchers who have actively contributed to the development of our knowledge on nutritional energetics during recent years.