How Can Intermittent Fasting Improve Your Sleep?

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Fasting & Sleep

This post originally appeared on oura's blog

Have you ever tried intermittent fasting? Trick question — we all fast naturally while we sleep. But a growing number of people are extending that period to change their daytime eating habits as well.

Keep reading to learn more about how fasting can impact your sleep and overall health. 

What Is Intermittent Fasting?

Intermittent fasting is an eating plan in which you consume food during specific times of day and then fast during the rest of the day. In practice, this commonly looks like an 8, 10, or 12-hour period of eating (sometimes called a “feeding window”) and the remainder of time is spent not eating, or fasting. 

For example, some people may follow a 16:8 schedule, in which they eat only during 8 hours of the day, and fast for the remaining 16 hours, including their sleeping period.

Another type of fasting is known as 5:2, in which someone limits their caloric intake by 25% for two days of the week, then consumes food as normal on the remaining days.

The point of this practice is for your body to enter into “fasting mode” and start converting your fat reserves into energy. 

Research shows that health benefits of intermittent fasting may include: 

  • Weight loss
  • Improved insulin sensitivity
  • Lower inflammation
  • Improved markers for heart disease 
  • Reduces risk of developing some cancers and some neurodegenerative diseases, such as Alzheimer’s and Parkinson’s

Fasting & Sleep

Fasting before bed may improve the quality of your sleep by supporting your natural circadian rhythms

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 lead to improved 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.

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.

Track Fasting With Cronometer

Gold subscribers have access to our Fasting Feature which helps you track your fasts and can provide valuable insights on how it’s impacting vital biometrics like sleep, weight, and appetite.

For example, if you’re not already, start tracking your sleep in Cronometer! The easiest way to do this is to connect a device which imports sleep, like the Oura Ring, or you can manually add a biometric.

There is a sleep duration biometric that already exists or Gold subscribers can create a Custom Biometric for sleep quality or something more specific. You can then create a chart to track that sleep data, click the three dot menu in the top right-hand corner of the chart and click ‘Show Fast Periods’ and you’ll see a visualization of how your fasting has impacted your sleep over time.

Keep In Mind

Some first-time fasters report disrupted sleep — the dreaded experience of lying wide awake in bed, bored and hungry. Why? Your “internal clocks” in your digestive tract are saying: “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.

Remember, every 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.

Start by experimenting with different protocols and observe what happens to your REM, deep sleep, and resting heart rate.

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