Have you ever tried fasting? Trick question. We all fast naturally while we sleep and a growing number of people are extending that period to change their daytime eating habits as well.
If you stop eating before sunset, you’re encouraging your body’s natural sleep pattern by “circadian fasting.”
When you go to bed with an empty stomach, the internal clocks in your digestive system align with the clock in your brain so that all your systems agree to go offline for sleep. This kind of fasting—which you can accomplish simply by eating dinner early and avoiding snacks before bed—can unequivocally improve your sleep.
If you’re embarking on a more complex fasting protocol, however, your digestive clocks need time to adjust to a new routine.
You may not see the improvements of fasting right away, but if you stick with it your body will adjust and your sleep patterns will normalize.
Fasting in the Short Term
Some first-time fasters report disrupted sleep—the dreaded experience of lying wide awake in bed, bored and hungry. Why is this?
Even though it’s dark outside and your body’s other clocks have called for bedtime, the clocks in your digestive tract are reporting back: “We haven’t eaten anything in a while! Are you sure we shouldn’t grab a bite to eat?”
As a result, your body might jump into action and produce the stress hormone cortisol to help keep you awake in case food walks by.
This is temporary—your body is simply getting used to a new routine. After an adjustment period that generally lasts about 3 to 7 days, your body steadies its rhythm and fasting can actually benefit your sleep.
Fasting in the Long Term
When you fast regularly, your body adapts to your new schedule and your circadian rhythm actually becomes more pronounced (in a good way). Intermittent fasting causes insulin levels to drop and melatonin levels to rise. Melatonin is your body’s primary sleep-promoting hormone and can help you fall asleep faster and stay asleep longer.
Fasting also promotes the release of human growth hormone, one of your body’s vital resources for repairs while you’re asleep.
Things to Keep in Mind
Everyone’s body adapts differently to food routines. If you aren’t planning to start doing serious intermittent fasting, start by paying attention to your dinner time and trying to finish up at least 2 hours before your bedtime.
If you are planning a more rigorous fasting routine, give yourself at least a week to adjust to a new habit.
Start by playing around with different protocols and observe what happens to your REM, deep sleep, and resting heart rate.
If your fast allows coffee, keep in mind that the timing of your caffeine may impact your sleep quality.
- Nakamura, Yuko, Brian R. Walker, and Toshikazu Ikuta. “Systematic review and meta-analysis reveals acutely elevated plasma cortisol following fasting but not less severe calorie restriction.” Stress 19, no. 2 (2016): 151-157.
- Longo, Valter D., and Satchidananda Panda. “Fasting, circadian rhythms, and time-restricted feeding in healthy lifespan.” Cell metabolism 23, no. 6 (2016): 1048-1059. (link)
- Peschke, Elmar, Ina Bähr, and Eckhard Mühlbauer. “Melatonin and pancreatic islets: interrelationships between melatonin, insulin and glucagon.” International Journal of Molecular Sciences 14, no. 4 (2013): 6981-7015. (link)
- Ho, Klan Y., Johannes D. Veldhuis, Michael L. Johnson, R. Furlanetto, William S. Evans, K. G. Alberti, and M. O. Thorner. “Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man.” The Journal of clinical investigation 81, no. 4 (1988): 968-975. (link)