1 · Every cell has a clock
Clock genes in every cell drive a 24-hour rhythm, synchronized by the suprachiasmatic nucleus, with light as the master zeitgeber and meal timing as the second.Nearly all metabolic enzymes, hormones, and transporters follow a 24-hour rhythm driven by core clock genes (CLOCK, BMAL1, PER, CRY) that self-oscillate in every cell, synchronized by the suprachiasmatic nucleus () in the hypothalamus.Light is the master zeitgeber; meal timing is the second. So when you eat directly resets liver and peripheral clocks.