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Evidence Based

Circadian Fasting: A Way to Restore the Body’s Natural Clock

Our natural circadian rhythm works to ensure that bodily functions are carried out at optimal times. There are many circadian rhythms running on a 24-hour schedule in our body, but the most well-known is the sleep-wake cycle.

Circadian rhythm fasting is an intermittent fasting style that aligns our eating times with the most optimal eating times for the body, usually during daylight hours when the food will be used for fuel.

Circadian rhythms play a major role in our health, and any disruption can lead to an increased risk of a number of illnesses—the circadian rhythm diet aims to minimize the disruption caused by the food we eat.

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What Is Circadian Fasting?

Circadian fasting is a time-restricted eating pattern wherein dieters eat the majority of their calories over a period in the earlier part of the day. Though there is no set time you should eat on this diet, most circadian rhythm dieters eat their meals between 8am and 6pm.

The circadian fasting method is sometimes referred to as the sun cycle diet, as dieters take their lead from sunlight hours. The goal of the fasting method is to time your eating with the rising and setting of the sun, which correlates with the rising and falling of cortisol levels in your body.

When the sun is up and the thyroid is stimulated, cortisol is released. When cortisol is released, your metabolism is awake too, and more likely to use the food you eat for fuel rather than store it as body fat.

Circadian rhythm fasting comes with many benefits for your health, including weight loss, increased metabolism, better energy levels, better digestion, and reduced inflammation.

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Circadian fasting vs. intermittent fasting

Intermittent fasting (IF) is a form of time-restricted feeding. There are many different types of the IF diet, including the 12-hour fast and the OMAD method. Like circadian rhythm fasting, IF restricts when you can eat.

The main differences between intermittent fasting and circadian rhythm fasting are:

  • Circadian rhythm fasting encourages dieters to take their lead from daylight hours, whereas IF dieters can choose when to fast and when to eat, no matter the position of the sun.
  • Intermittent fasting comes in many forms, including the 5:2 diet, which dictates a calorie restriction. The variety of different styles of IF makes it different from circadian rhythm fasting, which may be interpreted slightly differently but follows a general pattern.
  • Most people following a circadian rhythm fasting plan eat between the hours of 8am and 6pm. This means they fast for 14 hours at a time and rarely for longer. Depending upon your IF plan, you may be fasting for up to 24 hours at a time (like on the alternate-day fasting method).

How Does Circadian Fasting Restore the Body’s Natural Cycle?

Circadian rhythms in the body ensure that certain bodily functions are carried out at optimal times. The most well-known circadian rhythm is the sleep-wake cycle, which dictates when we feel tired and sleepy and when we wake up.

Circadian rhythms operate on a 24-hour cycle and disruptions can cause major issues with our health as well as increase our risk of a number of chronic diseases and metabolic disorders, including insulin resistance and diabetes.

A number of factors can lead to disruptions in our circadian rhythm, including sleep disorders, genetics, certain illnesses, and artificial lighting. Eating times can also affect circadian rhythms, particularly if you’re eating very late at night.

The circadian rhythm fasting diet can restore the body’s natural cycles by helping to realign the sleep-wake cycle. Eating late at night can disrupt REM sleep which can have a huge impact on hormone secretion and sleep quality, both of which disrupt circadian rhythms.

By eating during daylight hours and stopping eating as the sun sets, you can help to restore a proper sleep-wake cycle. Lack of sleep is associated with increased body weight, so, readjusting your sleep-wake cycle, and getting better sleep could help you to lose weight as well as restore your overall health.

Is Circadian Fasting Good for Weight Loss?

The main benefit of circadian rhythm fasting for weight loss is its impact on the sleep-wake cycle. As lack of sleep is linked to obesity, higher BMI, and overeating, restoring a better sleep-wake cycle and promoting healthier sleep can help with weight loss.

Weight loss during fasting is also increased by the following habit changes:

  • Consuming fewer calories
  • Controlling appetite
  • Improving metabolism

Fasting affects these changes by restricting the times at which dieters can eat.

Fasting causes people to eat fewer calories by shortening the periods they are allowed to eat. As it is physically impossible to eat as much in 8 hours as you would in 16 hours, shorter eating periods create a natural calorie deficit which helps people to lose weight.

Furthermore, longer periods without food help fasters curb their appetite and increase their metabolism. Indeed, fasting is thought to increase your metabolism by up to 14%.

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Other Proven Benefits of Circadian Fasting

Along with the weight loss benefits of circadian rhythm fasting, this kind of fasting may also have other benefits for your health. See below to find out more about how eating in time with your circadian clock can benefit you.

Better sleep

Circadian rhythm fasting helps to promote better sleep by encouraging you to stop eating at around 6pm. After you have eaten your final meal of the day, the body has a chance to digest the food properly before bed.

Eating food late at night has been shown to disrupt the sleep-wake cycle and overall quality of sleep.

Supports heart health

Research suggests that circadian rhythm fasting can play a role in reducing the risk of developing cardiovascular disease.

Further research suggests that circadian rhythm fasting has been linked to the reduction of a number of cardiovascular biomarkers, including blood pressure, cholesterol levels, triglyceride levels, and inflammation.

Gets the digestive system moving

Our circadian clock plays a significant role in digestive health and flourishing gut bacteria. For this reason, the circadian rhythm diet can help to get your digestive system back on track and increase regularity throughout.

Could increase longevity

Fasting for long periods has been associated with a boost in autophagy, the process by which cells are recycled, renewed, and replaced. Autophagy is inextricably linked to longevity.

Reduces the risk of health problems

Disruptions to the circadian rhythm can cause an increased risk of a number of chronic illnesses. For this reason, the circadian rhythm diet has been associated with a reduced risk of a number of health problems.

Circadian rhythm fasting has been shown to reduce biomarkers of chronic illnesses including heart disease and diabetes.

Are There Any Risks?

As with intermittent fasting, the circadian rhythm diet may not be suitable for some people due to the restrictive nature of the diet. People who have had, or still have, eating disorders should not follow the diet as it could lead to disordered eating patterns.

In addition, if you have to take certain medications with food, you may not be able to avoid eating outside of the required eating window.

While intermittent fasting and circadian rhythm fasting are considered safe, you should always speak with a doctor before trying any new diets. This is to assess any of the risks involved and to make sure it won’t exacerbate any illnesses.

5 Things to Know Before Starting Circadian Fasting

Before starting any time-restricted feeding diet, you should understand as much as possible about how it works. Below, we have summarized a few key things you should know about circadian rhythm fasting before trying it out yourself.

1. Eat your meals earlier in the day

The whole idea of circadian rhythm fasting is to eat while the sun is up. Cortisol levels are highest around 8am, meaning your metabolism is most active at this time. Eating earlier means that your body is more likely to use the calories you consume for fuel.

The calories used for fuel in your normal bodily processes are burned off quickly. The quicker this process (known as metabolism) the more likely you are to lose weight quickly.

2. Limit sugar and refined grains

As with any intermittent fasting diet, you’re not told what you can eat, but rather when you can eat. That being said, it is best to stick to a healthy and balanced diet during your eating window.

This means eating a diet filled with whole grains, fruits, vegetables, beans, legumes, lean protein, and healthy fats. This kind of food will keep you healthier in the long run and supports better metabolic health.

3. Stay active

Staying active is essential to your overall health. No matter your eating habits, the human body requires exercise. You should get at least 150 minutes of physical activity each week, equating to roughly 30 minutes a day.

Getting more active is great for weight reduction and can help limit weight gain.

4. Balance your sleep schedule with your eating schedule

A circadian fasting schedule does wonders for your sleep schedule which is why you should ensure you’re keeping a healthy sleep schedule., There is no point in using circadian rhythm fasting to boost your metabolic health and gut health, and then slacking when it comes to sleep quality.

If you struggle to sleep, you could try drinking chamomile tea, limiting screen time before bed, and diffusing lavender essential oil. You could also keep your bedroom cool as sleep is linked to body temperature.

5. Avoid artificial light in the evening

Artificial lighting, particularly the blue backlight from screens, can cause disruption to your circadian rhythm by stimulating the production of melatonin. Melatonin production is inhibited by light and so reducing light in the evenings and avoiding screens can help to balance your circadian clock.

Start Circadian Fasting With DoFasting

Circadian rhythm fasting and intermittent fasting go hand in hand. For that reason, DoFasting is the perfect companion to your circadian rhythm fasting diet. The DoFasting app is a well-rounded tool for fasting beginners.

The app provides a place for you to track your progress, your food intake, and even your water intake. It also offers fasting-friendly recipes and workouts along with educational articles on the benefits of fasting.

You’ll be able to use the DoFasting fasting timer to remind you when to start and when to stop fasting, and you can get to know other fasting methods, like the 16:8 method and the 24-hour fast.

Circadian rhythm fasting uses the body’s internal clock to promote weight reduction, but the DoFasting app can be a useful companion on this journey.

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Circadian Fasting: Final Thoughts

Circadian rhythm fasting is a time-restricted eating schedule that has many health benefits. It uses the rise and fall of the sun to dictate your eating window and has been known to help people to reduce their body weight.


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This is an evidence-based article that includes scientific citations. DoFasting’s professional writers and editors prepared the content, which a team of medical experts verified to be accurate.

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