Diet-induced changes in sympathoadrenal activity: Implications for thermogenesis and obesity

Evidence is reviewed in support of the concept that adaptive changes in thermogenesis accompany changes in dietary intake. Undernutrition is associated with diminished metabolic rate and increased efficiency of caloric utilization and storage; increased caloric intake or overfeeding is associated with an increase in metabolic rate and dissipation of excess calories as heat. Since the sympathetic nervous system has an important role in the regulation of thermogenesis the possibility that diet-induced alterations in sympathetic activity are responsible for adaptive changes in thermogenesis is explored. Evidence that fasting suppresses and overfeeding increases the activity of the sympathetic nervous system is reviewed; the data are consistent with a major role for sympathetic activity in the coupling of dietary intake with metabolic rate. Insulin may be an important signal in coupling changes in dietary intake with changes in sympathetic activity. Diet-induced changes in sympathetic activity may have important implications for the development of obesity and for the association of obesity with cardiovascular disease.