We have explained that the ventrolateral subdivision of the suprachiasmatic nucleus (SCN) might be the substrate for central regulation of energy metabolism. Both nocturnal and diurnal animals eat not only to provide glucose to the brain, but also to provide glucose to other parts of the body during their active period. During the animals’ resting or sleeping period, however, gluconeogenesis is required to take place because of limitations on the amount of glycogen which can be stored in the liver. We presented evidence that obesity resulted from hypofunction of the SCN, and the associated enhanced secretion of insulin and suppressed secretion of glucagon. Several lines of evidence have indicated that besides central regulation of energy metabolism the SCN might also be involved in the regulation of blood pressure, thermogenesis, and glucocorticoid secretion. We should further encourage vigorous efforts to decrease pollutants which interfere with light emitted from the sun.