CHRONOBIOLOGY AND MEAL TIMES - INTERNAL AND EXTERNAL FACTORS

Although homeostatic mechanisms remain of utmost importance, rhythmic changes are present also. The main ones have a period of 24 h (circadi an) or about 2-3 h (ultradian). Circadian rhythms are derived from a b ody clock, found in the base of the brain, and from the pattern of our sleep wake cycle, including activity and meal times. These rhythms pr omote the regular changes between an active wake period and a recupera tive sleep period. Ultradian rhythms are also widespread and reflect e xternal (lifestyle) and internal factors. The internal factors include biochemical need and some sort of oscillator; but details of how many oscillators, and exactly where they are, remain to be established. Fo od intake, appetite, digestion and metabolism have been shown to illus trate these principles. Moreover, these principles become important wh en special circumstances exist as far as meal times are concerned; the particular difficulties of night workers is a good example.