Eating four hours later doubled the odds of hunger

Researchers at Brigham and Women's Hospital put the same adults through two tightly controlled weeks, one on an early meal schedule and one on a late schedule, while holding food, sleep, light and activity identical.

Late eating doubled the odds of feeling hungry and shifted appetite hormones toward wanting more food, raising the ratio of ghrelin to leptin by 34 percent during waking hours. It also lowered energy expenditure while awake and dropped 24-hour core body temperature, two signs of a body burning calories more slowly.

Fat tissue samples showed late eating altered genes involved in fat storage, shifting the balance toward building fat rather than breaking it down. Every variable but meal timing was controlled, which is the trial's strength and its limit at once, since the sample was small and the effect of timing alone in free-living conditions, with normal variation in sleep and activity, is still being tested.

The clock on the wall, not just the plate.