80% of the genes in your body and brain are on a 24-hour schedule. That is, they change their levels going from high to low and back to high again across the 24-hour cycle. And when those genes are high at the appropriate times and low at the appropriate times... your health benefits. When those genes are not expressed at the right times—when they're high or low at the wrong times of each 24-hour cycle—that's when you get negative health effects.