Quick answers
Intermittent fasting for shift workers
Night shifts, rotas and 24-hour shifts: how to time your eating window around your sleep
Why shift work is hard on your metabolism
Your body clock expects food during the day. In a laboratory study, the same meal raised blood sugar 17% more at 8 p.m. than at 8 a.m., and flipping people's day and night, as night work does, raised it by another 6% 2. Meals also help set the clocks in your organs: when young men ate 5 hours later, their blood sugar rhythm shifted by about 5 and a half hours 3.
Key study
Daytime eating protected blood sugar during night work
- Randomized lab study
- 19 healthy young adults
- 14 days
During simulated night shifts, people who ate at night handled sugar worse, and their body clocks fell out of step with each other. People who kept their meals to the daytime avoided both. It was a short laboratory study, but it points to a simple habit.
Chellappa et al., Sci Adv 2021A trial in real shift workers
Key study
A 10-hour window for firefighters
- Randomized trial
- 137 firefighters
- 12 weeks
Firefighters on 24-hour shifts cut their eating window from about 14 to 11 hours, with no adverse effects and better quality of life. In those at higher risk at the start, long-term blood sugar (HbA1c) and diastolic blood pressure fell compared with usual care.
Manoogian et al., Cell Metab 2022Only 9% of the firefighters were women, and one trial can't cover every rota, but it's encouraging evidence that a steady window can fit shift work.
Sample schedules
| Shift | Main sleep | Eating window | Fast |
|---|---|---|---|
| Days, 7:00 a.m. to 3:00 p.m. | 10:00 p.m. to 5:30 a.m. | 6:00 a.m. to 6:00 p.m. | 12 hours |
| Evenings, 3:00 p.m. to 11:00 p.m. | 12:30 a.m. to 8:30 a.m. | 9:30 a.m. to 7:30 p.m. | 14 hours |
| Nights, 7:00 p.m. to 7:00 a.m. | 8:30 a.m. to 3:30 p.m. | 4:00 p.m. to 1:00 a.m. | 15 hours |
| 24-hour shifts | Whenever you can | The same 10 to 11 hours every day, such as 8:00 a.m. to 6:00 p.m. | 13 to 14 hours |
| Days off after nights | A short nap, then a normal night | 10:00 a.m. to 7:00 p.m. | Back to a daytime rhythm |
On nights, the idea is to eat your main meal before the shift, keep the small hours light or food-free, and fast through your daytime sleep. If hunger hits late in the shift, a small protein snack is better than struggling: a longer plan such as 16:8 can wait for your days off.
Driving home safely
Night shifts make driving more dangerous. When 16 night-shift workers drove on a closed test track, 6 of 16 drives after a night shift had near-crashes and 7 were stopped early for safety, compared with none after a night's sleep 5.
- Don't stretch a fast over the drive home if you feel shaky, lightheaded or unusually tired: eat something first.
- If you're drowsy, don't drive. Take a short nap first, or get a lift or public transport.
- Stop and eat if you feel dizzy, confused or faint at any point in a shift.
Time your caffeine for your sleep
Coffee helps at the start of a night shift, and black coffee doesn't break a fast. But time it for your sleep, not the clock: 400 mg of caffeine taken even 6 hours before bed still disturbed sleep in a home study 6. If you go to bed at 8:30 a.m., have your last coffee by about 2:30 a.m. See coffee and fasting.
Fasting Tracker for shift work
Fasting Tracker's timer starts whenever you do, so your fast doesn't have to begin in the evening. If you forgot to start it after a meal, back-date the fast or edit its start time; you can also end a fast at a different time, or log a past fast after a long shift. The free plans run from 13 to 18 hours, Pro adds custom fasts from 12 to 72 hours, and you can start or end a fast with Siri.
Sources
- Manoogian ENC, Zadourian A, Lo HC, et al. Feasibility of time-restricted eating and impacts on cardiometabolic health in 24-h shift workers: The Healthy Heroes randomized control trial. Cell Metab. 2022;34(10):1442-1456.e7. doi.org/10.1016/j.cmet.2022.08.018
- Morris CJ, Yang JN, Garcia JI, et al. Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans. Proc Natl Acad Sci U S A. 2015;112(17):E2225-34. doi.org/10.1073/pnas.1418955112
- Wehrens SMT, Christou S, Isherwood C, et al. Meal Timing Regulates the Human Circadian System. Curr Biol. 2017;27(12):1768-1775.e3. doi.org/10.1016/j.cub.2017.04.059
- Chellappa SL, Qian J, Vujovic N, et al. Daytime eating prevents internal circadian misalignment and glucose intolerance in night work. Sci Adv. 2021;7(49):eabg9910. doi.org/10.1126/sciadv.abg9910
- Lee ML, Howard ME, Horrey WJ, et al. High risk of near-crash driving events following night-shift work. Proc Natl Acad Sci U S A. 2016;113(1):176-81. doi.org/10.1073/pnas.1510383112
- Drake C, Roehrs T, Shambroom J, et al. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med. 2013;9(11):1195-200. doi.org/10.5664/jcsm.3170
- Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. doi.org/10.3390/nu11040873
Keep reading
Your body clock: when you eat mattersWhy the same meal affects you differently in the morning and at night, and how to choose your eating window
Sleep and fastingHow sleep shapes your hunger, whether fasting affects your nights, and how to time your last meal- Intermittent fasting calculatorEnter when you last ate and your plan, and see when you can eat again, when your eating window closes and the stages on the way
A note on health
Fasting Tracker is designed for general wellness and is not a medical device. Fasting is not right for everyone. If you are pregnant, diabetic, have a history of eating disorders or take medication, talk to your doctor first, and before any extended fast.