Why Do Graveyard Shifts Wreak Havoc on Human Metabolism?

Humans are wired to be awake during the day and sleep at night, but millions of Americans defy biology to pull the graveyard shift. Hospital employees, firefighters and, increasingly, office workers all punch in for nighttime work. These nocturnal schedules appear to be one driver of the rising rates of obesity and metabolic disorders. Yet exactly how swapped slumber time fuels metabolic disarray has largely mystified sleep researchers.