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Contents
What is Circadian Fasting?
Circadian fasting is a type of fasting that follows the body’s natural daily rhythm, known as the circadian rhythm.
This means eating during specific time windows, typically aligned with daylight hours, and fasting during the remaining hours, allowing the body to align its eating patterns with its natural biological clock.
It’s a way of syncing eating habits with the body’s internal clock for potential health benefits.
Circadian Fasting is a form of intermittent fasting.
Why is Circadian Fasting Imporant?
Humans tend to eat during the day and fast during the night, which is a basic form of intermittent fasting.
During Circadian fasting, you have a 12-hour period where you are allowed to eat food and 12 hours where you are not. This eliminates any nighttime snacks or midnight sprints to the fridge.
Meal sizes are also different, with breakfast being the largest meal and dinner being the smallest. This will benefit your nighttime sleep quality as it aligns your eating with your circadian clock.
Benefit #1: Improved Metabolism
Circadian rhythm fasting confines meals to the earlier hours of the day, restricting the hours of the day you eat rather than the amount you eat. This practice can synchronize appetite with circadian rhythm and improve metabolism.
Benefit #2: Enhanced Weight Control
Studies show that overweight people have a smaller appetite when they are practising Circadian Fasting. This is because the times you are eating are parallel to the times certain hormones are released. This means overweight people will go into a calorie deficit naturally when they feel less inclined to eat a lot.
Benefit #3: Better Sleep Quality
Circadian fasting offers potential improvements to sleep quality by aligning with the body’s natural rhythm. The regulation of melatonin production is a key factor, as fasting during nighttime hours supports the body’s natural increase in this sleep-promoting hormone. Establishing a consistent circadian fasting routine helps to normalise the body’s sleep-wake cycle, creating more predictable and restful sleep patterns.
Benefit #4: Increased Insulin Sensitivity
According to Jefferson Health, “Fasting for at least 16 hours gives the body a chance to rest and allows blood levels of insulin to drop significantly. Not only does this help burn fat, it can also lower your risk of disease, particularly diabetes and pre-diabetes.”
Benefit #5: Immune System
The circadian rhythm regulates the immune system function, influencing factors like inflammation and the body’s response to infections.
This means that Circadian Fasting will help prevent you from getting sick and help you recover when you are ill.
Benefit #6: Digestive Health:
Allowing the digestive system to rest during the fasting period may improve digestive health, reducing the strain on the digestive organs.
Benefit #7: Promotion of Cellular Repair:
Fasting periods allow the body to engage in cellular repair processes, which helps with overall tissue maintenance and regeneration.
Benefit #8: Optimized Hormonal Balance:
Circadian fasting may contribute to a balanced release of hormones, such as cortisol and melatonin, which support overall hormonal health.
Benefit #9: Adaptation to Natural Rhythms:
Circadian fasting aligns with natural biological rhythms, which allows the body to function more efficiently and adapt to its evolutionary patterns.
Circadian Rhythm
Before we learn how to implement Circadian Fasting, we must first learn what this concept is based on and how it works.
It is the body’s internal clock that helps regulate various functions over 24 hours. It influences processes like:
- Sleep-Wake Cycle
- Hormone Secretion
- Body Temperature
- Metabolism
- Cellular Repair and Maintenance
- Cognitive Function
- Digestive Processes
- Mood and Emotions
- Cardiovascular Function
- Immune System Function
This internal clock is influenced by external cues like light and darkness, helping us stay synchronized with the natural day-night cycle.
Implementing Circadian Fasting
Implementing Circadian Fasting involves adjusting your eating patterns to align with your body’s natural circadian rhythm.
You typically eat only for 12 hours, usually 7 a.m. to 7 p.m. and fast for the rest of the 12 hours.
Meal sizes are also flipped:
Breakfast becomes your biggest meal and dinner becomes your smallest.
Here are 8 actionable steps you can do to help implement this process:
Step 1: Understand Your Natural Rhythms
Your first step is to acknowledge the cyclical nature of the day. Recognise that daylight signifies wakefulness and activity, while darkness signifies rest and recovery for our bodies. This cycle is deeply ingrained in the biology of humans.
You also need to recognise that the morning is when you are most alert and you should schedule important tasks to be completed in this period to increase your productivity. The evening is the complete opposite, and reducing levels of daylight sinals to the body to start to wind down and relax. This means you should schedule for less draining and more comfortable tasks to be done in the evening.
Spend time outdoors during daylight hours to maximize exposure to natural light. Sunlight is a primary regulator of the body’s circadian rhythm, influencing the production of hormones like serotonin that promote wakefulness.
Step 2: Adjust your day to your natural rhythms
Some people may naturally be more productive in the mornings whilst others prefer working at night when the sun’s down. Everyone has different periods during the day where their focus levels are at the highest and therefore you can be the most productive.
This means you need to adjust your routine to suit your needs.
For example, I prefer working in the late morning/afternoon because I find that this is the time I can be most productive and get the most done.
Step 3: Establish A Consistent Eating Window
Choose a specific eating window in the daylight hours for your eating. This period must be 12 hours, with the other 12 hours reserved for your fasted state. The most common window people tend to choose is from 7 a.m. to 7 p.m.
You also want to avoid late-night eating and try to have your last meal at least 2 hours before your bedtime (This means no snacks too!)
Step 4: Prioritize Breakfast
Have a large breakfast so that you are ready for the day. This will be your biggest meal.
Step 5: Stay Hydrated
It is so important to stay hydrated throughout the day because staying hydrated has links to your mood, energy and other health benefits. This is even more important when you are in a fast state so drink a lot of water. Drinking lots of water also helps reduce the feeling of hunger when you are fasting.
Step 6: Be Consistent
Be consistent with your eating patterns so that your body can anticipate when you will eat. This helps your body establish a predictable rhythm. For example, if you tend to have breakfast at 7 a.m., try to have breakfast at 7 a.m. every day.
Step 7: Reflect and Improve
Reflection is key to improvement because when you can see where there are areas that are not working so well, you can change them so that you further optimise your circadian rhythm and productivity.
For example, if you think your optimal working time is in the evening, but at night, all you can think about is Game Of Thrones, then you might consider changing your important working period to an earlier time.
Step 8: Create Your Daily Routine
The final step is to create your daily routine and this will help you stay on track and not stray off course.
To create your routine, answer these questions:
- What time do you wake up?
- What are the most important tasks that need to be done?
- When is your optimal time for working?
- What are the less important tasks that you need to do?
- What time do you go to bed? (You need a minimum of 7 hours of sleep to be productive, preferably 8)
Once you have answered those questions, write out a rough outline of what you want your day to look like. Here’s an example:
Morning – Wake up at 6 a.m. and workout
Be at my desk ready to work at 8
Get the most important work done between 8 and 4 p.m.
Get less important work done in the evening. (Requires less focus)
Relax and get to bed at 10.
I just want to emphasise the importance of waking up early because I have found that this little trick alone has boosted my productivity 10 fold. You can find a guide on how to wake up early and become a morning person here.
Relaxation is also very important and you need to take time for yourself so that you don’t burn out.
So write down your daily routine and let’s move on to the next chapter: Circadian Fasting Vs. Intermittent Fasting.
What is Intermittent Fasting?
Intermittent fasting is a type of fasting that involves cycling between periods of fasting and eating. There is no set time for each period, but you have to be consistent about what periods you eat, and what periods you fast.
Pros and Cons of Intermittent Fasting
| Pros | Cons |
|---|---|
| Blood Sugar Control | Potential Hormonal Changes |
| Improved Metabolism | Potential Nutrient Difficiency |
| Inflammation Reduction | Not Suitable For Everyone |
| Productivity | Potential Eating Disorder |
| Weight Loss | Potential of Overeating |
Difference Between Intermittent Fasting and Circadian Fasting
Intermittent Fasting
Definition: Intermittent fasting involves cycling between periods of eating and fasting. It doesn’t involve specific food choices but instead focuses on when you eat.
Timing: The amount of time you fast for can differ, but common methods include the 16/8 method (16 hours of fasting, 8 hours of eating), 5:2 method (eating normally for five days and significantly reducing calorie intake for two non-consecutive days), or the eat-stop-eat method (24-hour fasts once or twice a week).
Flexibility: Intermittent fasting is often more flexible, allowing individuals to choose the fasting and eating windows that suit their lifestyle.
Circadian Fasting:
Definition: Circadian fasting is based on aligning eating patterns with the body’s natural circadian rhythm, which follows a roughly 24-hour cycle. It emphasizes eating during daylight hours and fasting during the evening and nighttime.
Timing: This approach suggests that the body is more efficient at processing food during the daytime, aligning with the body’s natural wake-sleep cycle.
Light Exposure: Circadian fasting also considers exposure to natural light, emphasizing exposure to sunlight during the day and minimizing exposure to artificial light at night, as light exposure influences circadian rhythms.
Now that you understand the difference between intermittent fasting and circadian fasting, let’s move on to who should try doing Circadian Fasting.
Factors To Consider Before Trying Circadian Fasting
Sleep: Sleep is an essential part of our health and is key to us being productive. It is also closely linked with our body’s circadian rhythm as it controls our body’s sleep-wake cycle.
Lifestyle & Schedule: Choose a fasting period that suits your commitments and adjust it based on your availability.
Nutrient Timing: Make sure that your fasting window lets you consume the necessary nutrients to stay healthy.
Hydration: Staying hydrated is important regardless of what you do but it is even more important when you are fasting.
Physical Activity: Make sure you adjust your fasting period so that you have enough energy before and after exercise, especially if you are doing intensive training.
Consider The Pros & Cons of Circadian Fasting:
| Pros | Cons |
|---|---|
| Circadian Rhythm Alignment | Difficulty in Maintaining Lifestyle |
| Optimized Digestive Function | Potential Nutrient Deficiency |
| Enhanced Cellular Repair and Longevity | Negative Impact on Physical Performance |
| Weight Management | Risk of Disordered Eating |
| Improved Metabolic Health | Potential Negative Impact on Metabolism |
Pros & Cons Of Circadian Fasting
I have already covered the pros of circadian fasting but I will go over them quickly again. To see more about the pros, go here.
Circadian Rhythm Alignment: Circadian Fasting aligns eating with your circadian rhythm which may have health benefits. This alignment may improve sleep quality, hormonal balance, and various bodily functions. This also has benefits for your productivity as benefits such as sleep quality may increase your energy levels, leading to your productivity levels increasing.
Optimized Digestive Function: Fasting periods allow for your digestive system to rest and recover. This can improve your digestive function, reduce inflammation and increase nutrient absorption when eating.
Enhanced Cellular Repair And Longevity: Fasting periods allow for your body to focus on cellular repair processes and this may lead to better longevity.
Weight Management: Circadian Fasting can help manage your weight because it promotes a more balanced energy intake. Fasting periods can help limit calorie intake, reduce random snacking and help reduce or maintain weight.
Improve Metabolic Health: Although more research is required, some studies suggest that restricting food intake to specific time windows can help regulate blood sugar levels, improve insulin sensitivity, and reduce the risk of metabolic disorders like type 2 diabetes.
Let’s go over the negatives:
Difficulty In Maintaining Lifestyle: If you are busy or have an inconsistent schedule such as having to attend lots of events, irregular work schedules or other commitments, then circadian fasting may not be possible for you.
Potential Nutrient Deficiency: If you do not plan well, a shortened eating period may mean that you don’t get the required nutrients in you.
Negative Impact on Physical Performance: For normal individuals this shouldn’t be a problem, however, if you are a high-level athlete who is exercising at a high or intense level, not consuming energy during fasting periods may hinder your performance.
Risk Of Disordered Eating: Certain individuals are more prone to developing disordered eating which is a possibility when trying circadian fasting.
Potential Negative Impact on Metabolism: Although more research is needed, some studies suggest that prolonged fasting periods could lead to the body slowing down its metabolic rate, which may hinder weight loss in the long run.
As with most things, there will always be positives as well as negatives. However, if managed correctly, circadian fasting should not cause any serious damage to your health. If you are unsure about trying, it is always best to consult a professional to see if this could fit you.
Who Should Try Circadian Fasting?
Circadian fasting is a great way to improve your productivity as it has certain health benefits such as improved sleep quality that will contribute to you having more energy to be productive and get work done.
This means it is especially suitable for individuals who are looking to be more focused during their work, be more productive, improve sleep quality, improve metabolic health, people looking to manage weight and people who have a consistent daily routine.
When Should You Fast
I would recommend that you follow your circadian fasting cycle based on the diagram above. Have breakfast at 9:00 and lunch somewhere between 9:00 and 18:00. Then have your last meal at 19:00 and start fasting after that. This aligns your fasting and eating periods with a typical person’s circadian rhythm.
However, you should take this as a general guideline and adjust it as you see fit. Some people may have commitments or certain circumstances where this schedule isn’t suitable for them (for example people who work night shifts) so you should adapt it to fit around your schedule.
Now It's Your Turn
This is the ultimate guide to circadian fasting.
Now I want to turn it over to you: Will you be trying out Circadian Fasting? Was there anything I missed in this article?
Let me know by leaving a comment below right now.