People may initially notice minor sleep disturbances when starting intermittent fasting. This usually subsides within a week as the body adjusts to the new schedule.
After this period, most people report improved sleep quality when fasting, especially when they synchronize the timing of meals with the body's natural sleep circadian rhythm.
If you're new to intermittent fasting, download the WeFast - Intermittent fasting app to get started.
Are you up at night tossing and turning, wishing you could shut your brain off and catch some Z's?
Sleep disturbances are widespread, especially among women. According to the National Sleep Foundation, 67% of females reported issues with sleep a couple of nights a week, and 46% had problems every night (1). Intermittent fasting may provide a solution to falling and staying asleep.
If you're new to intermittent fasting, download the WeFast - Intermittent fasting app to get started.
Circadian rhythms create changes in the body and run on a 24-hour repeating cycle. These patterns work behind the scenes of different body functions and processes such as hormone release, eating habits, digestion, and body temperature. The most noticeable circadian rhythm is the sleep-wake cycle (2).
Our internal or biological clocks are the body's natural timing systems that regulate circadian rhythms. Almost every tissue and organ has its own clock. The central clock in the brain that coordinates the other clocks is called the suprachiasmatic nucleus (SCN) and is found in the hypothalamus. The hypothalamus is the mood and sleep center of the brain. The SCN coordinates all the clocks based on the eyes perceiving light or dark (2).
The production of the sleep hormone melatonin is controlled by the SCN. When there is less light at nighttime, the SCN signals the brain to trigger the release of melatonin, and you start to get drowsy. Melatonin levels drop during the day (3).
Whether you realize it or not, you are already fasting every day. While you sleep, your body fasts. When you wake and eat, you break the natural fast.
Intermittent fasting means extending the hours of that natural, daily sleeping fast. Eating and sleep routines are interconnected. Whether you choose to follow a 16/8, 5:2, alternate day, OMAD or another method of intermittent fasting, if you stop eating as the sun sets, you can align your digestive and sleep internal clocks and get a good night's sleep according to your natural circadian rhythm. Unfortunately, many people eat late at night or right before bed, and the clocks get confused.
The brain is being told by the dimming light to go to sleep, but the digestive system is being woken up and kicked into action, leaving you staring at the ceiling at 3am.
Intermittent fasting and sleep quality are connected. When you follow set mealtimes, it promotes a better sleep-wake cycle. Timing your intermittent fasting meals to coincide with your natural circadian rhythm has many benefits for improving your sleep.
Download the WeFast - Intermittent fasting app to kick-start those benefits, WeFast was designed for women only.
Both melatonin and fasting impact the body's production of insulin.
Insulin regulates blood sugar levels. When you eat, blood sugar levels rise, and insulin is released. The food consumed is converted to energy for the body. But if you consume more than your body needs, the excess is stored as fat. When your body is in a fasted state, insulin levels are very low, and the body turns to the stored fat to burn for energy (4).
Insulin is produced by the pancreas. The pancreas is highly sensitive to melatonin. Because you are fasting when you sleep, the body doesn't need high insulin levels to deal with rising blood sugar. Melatonin binds to receptors in the pancreas, slowing down insulin production (5). As mentioned, insulin levels are also significantly lowered with intermittent fasting. Incorporating fasting into your daily routine – with timed meals ending before it gets dark outside – reduces your insulin levels significantly and increases melatonin levels, allowing you to fall asleep easier and stay asleep longer.
One of the bonuses of intermittent fasting is that it triggers the production of the human growth hormone, which naturally depletes with age (6). The human growth hormone (HgH) is produced during sleep and has amazing benefits for the body, including:
People who adopt an intermittent fasting lifestyle will have higher levels of HgH. Those who fast often report a more restful night's sleep and wake up feeling refreshed and energized.
It doesn't take much time for intermittent fasting to positively impact sleep. One study showed that after a week of intermittent fasting, people woke up in the night less frequently, moved around in their sleep less, spent more time in the deep REM stage of sleep, and reported better overall sleep quality (7).
But for some intermittent fasting beginners, sleep will be disrupted initially as the body adjusts to this new eating routine. Your master biological clock may be telling you that it's time for sleep when it gets dark, but your internal digestive clock is still on your old eating schedule. The body is on alert, waiting for you to feed it, and as a result, it may release the stress hormone cortisol to keep you awake.
Choose an intermittent fasting eating schedule that ends in the early evening, be consistent, and your body will quickly adjust.
Intermittent fasting may temporarily disrupt sleep while the body adjusts to the new eating schedule. Timing meals to coincide with the body's natural circadian rhythm by eating when it's light out and fasting once dark can significantly improve your overall sleep quality. Avoid eating at least 3 hours before bed, stay hydrated, and choose nutrient-dense foods to sleep soundly through the night.
Join our online community of intermittent fasting women for more sleep-promoting ideas and support.
1. NSF 2007 Sleep in America poll. WB&A Market Research. 2007. https://www.sleepfoundation.org/insomnia/insomnia-women
2. Circadian Rhythm, National Institute Of General Medical Sciences. https://www.nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx
3. Doghramji K. Melatonin and its receptors: a new class of sleep-promoting agents. J Clin Sleep Med. 2007;3(5 Suppl):S17-S23.
4. Cho Y, Hong N, Kim KW, et al. The Effectiveness of Intermittent Fasting to Reduce Body Mass Index and Glucose Metabolism: A Systematic Review and Meta-Analysis. J Clin Med. 2019;8(10):1645. Published 2019 Oct 9. doi:10.3390/jcm8101645
5. Sharma S, Singh H, Ahmad N, Mishra P, Tiwari A. The role of melatonin in diabetes: therapeutic implications. Arch Endocrinol Metab. 2015;59(5):391-399. doi:10.1590/2359-3997000000098
6. Ho KY, Veldhuis JD, Johnson ML, et al. Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man. J Clin Invest. 1988;81(4):968-975. doi:10.1172/JCI113450
7. Michalsen A, Schlegel F, Rodenbeck A, et al. Effects of short-term modified fasting on sleep patterns and daytime vigilance in non-obese subjects: results of a pilot study. Ann Nutr Metab. 2003;47(5):194-200. doi:10.1159/000070485
8. Asher Y Rosinger, Anne-Marie Chang, Orfeu M Buxton, Junjuan Li, Shouling Wu, Xiang Gao, Short sleep duration is associated with inadequate hydration: cross-cultural evidence from US and Chinese adults, Sleep, Volume 42, Issue 2, February 2019, zsy210, https://doi.org/10.1093/sleep/zsy210
9. Spadola CE, Guo N, Johnson DA, et al. Evening intake of alcohol, caffeine, and nicotine: night-to-night associations with sleep duration and continuity among African Americans in the Jackson Heart Sleep Study. Sleep. 2019;42(11):zsz136. doi:10.1093/sleep/zsz136
