Circadian Misalignment Increases 24‑h Acylated Ghrelin in Chronic Shift Workers (Randomized Crossover)
Summary
This small randomized crossover study tested seven healthy chronic night-shift workers in a lab for two 3-day conditions: a day-work (aligned) schedule and a night-work schedule with a 12-hour inversion (circadian misalignment). With diet kept constant, misalignment increased 24-hour acylated ghrelin by ~17%, a hormone that stimulates appetite. Participants also felt ~14% hungrier at “breakfast” on the misaligned schedule. Energy expenditure and respiratory exchange ratio didn’t change, meaning they didn’t burn more calories. Interestingly, overall activity was ~38% higher during misalignment even though sleepiness also increased. These are acute effects measured over a few days in a small sample, so the study does not prove long-term weight gain—but it shows that circadian misalignment can raise hunger signals in actual shift workers.
Why It Matters For Night Shift Workers and Night Owls
When your schedule is flipped, your body may turn up appetite hormones even if you’re not burning more energy. That’s why nights can feel snacky—it’s physiology, not a lack of willpower. Practical moves: pre-plan a steady “breakfast” and first-half-of-shift meal, emphasize protein + fiber to blunt hunger, keep hydration up, and set default snack portions so hormone-driven cravings don’t snowball. Since the effect showed up quickly, these strategies are most helpful on misaligned weeks or during schedule switches.
Notes
Full text: https://onlinelibrary.wiley.com/doi/full/10.1002/oby.23838