Circadian Rhythm Fasting: What to Know
There has been growing interest in intermittent fasting in recent years. This practice, which involves only eating during a specified period of time, has been shown to have numerous health benefits. These include boosting memory, improving heart health, increasing fat burning, improving blood sugar regulation, and reducing insulin resistance.
Another benefit of fasting involves syncing meals with the circadian rhythm. The circadian rhythm is a 24-hour internal clock that regulates several processes in our body, including the sleep/wake cycle. It’s thought that syncing mealtimes with the body’s natural rhythms can help prevent chronic diseases that are associated with disrupted sleep/wake cycles.
Read on to learn about the different types of intermittent fasting, the benefits of fasting, and strategies for syncing your mealtimes to your natural circadian rhythm.
Understanding Intermittent Fasting
While many diets focus on what to eat, intermittent fasting focuses on when you eat. When you follow intermittent fasting, you only eat during a specific time of day. There are many different fasting protocols, such as:
5:2 diet. This involves eating normally for five days of the week and eating up to 25% of your calorie needs on fasting days.
Time-restricted feeding. This involves eating during a “food window” that lasts several hours. The most common version of this type of eating is the 16:8 diet (fasting for 16 hours, followed by eating for eight hours). Circadian fasting (matching your mealtimes to your sleep/wake cycle) is a type of time-restricted feeding.
Complete alternate-day fasting. Alternates fasting days with eating days.
Religious fasting. Fasting that is undertaken for religious or spiritual reasons.
Of all the fasting protocols, time-restricted feeding (and in particular, circadian fasting) is the most “natural,” as it syncs mealtimes to the sleep/wake cycle.
Benefits of Fasting
Some of the main benefits of fasting are related to cell repair and the immune system. Two such benefits include fasting’s effects on controlled cell death and reducing inflammation in the body. There may also be benefits to the gut microbiota.
Fasting and Autophagy
One of the main benefits of fasting is its effect on autophagy. Autophagy is an important process during which cells in the body break themselves down to allow for the removal of incorrectly produced or clumped proteins, as well as the recycling of damaged cell components. It can be thought of as the “clean up” system of the body.
Studies show that fasting helps activate the process of autophagy. This is beneficial, as autophagy plays an important role in the normal function of cells.
Fasting and the Immune System
Fasting also has a beneficial effect on the immune system. A study looking at the effect of fasting on monocytes (a type of immune cell associated with inflammation) found that fasting led to reduced amounts of monocytes in the blood.
Fasting also led to reductions in metabolic activity and genes associated with chronic inflammation. In other words? Fasting helped reduce inflammation in the body without compromising the body’s ability to fight off infections.
Another study found that fasting promotes the regeneration of immune cells. It’s thought that this occurs because fasting promotes the self-renewal of hematopoietic stem cells, a type of stem cell that can produce immune cells.
Overall, fasting plays an important role in the normal functioning of the immune system.
Fasting and the Gut Microbiota
Another benefit of fasting is its effects on the gut microbiota. The gut microbiota is the community of microorganisms that inhabit the gut. Studies show that intermittent fasting increases the diversity of the gut microbiota. This is beneficial, as increased microbiota diversity is a marker of a healthy gut.
The study also found that certain types of bacteria flourished during intermittent fasting. The types of bacteria that proliferated during fasting were butyrate-producers. Butyrate is a short-chain fatty acid with health-promoting effects, such as regulating fluid transport through cells, reducing inflammation of the gut barrier, increasing the integrity of the gut barrier, and regulating muscle contractions in the intestines.
Understanding Circadian Rhythm
The circadian rhythm is a 24-hour internal clock in our brain that controls several important processes in the body, including when we feel tired and when we feel alert. It does this by responding to light changes in our environment.
In vertebrate animals (including humans), the master clock is a group of 20,000 nerve cells that make up the suprachiasmatic nucleus (SCN). The SCN receives input from the eyes, making it sensitive to changing light levels. When it’s light out, the SCN sends signals telling you to wake up. When it’s dark out, the SCN sends signals telling you to wind down for bed. This is what controls the sleep/wake cycle.
It’s essential that we maintain a healthy sleep/wake cycle because many important aspects of human health, such as memory, healing, and metabolic regulation, occur during the sleep cycle.
In addition to its role in sleep and wakefulness, the circadian rhythm also influences eating habits, digestion, body temperature, and hormone release.
It’s important to maintain a healthy circadian rhythm. Some of the things that may disrupt circadian rhythm include:
Mutations in genes related to our biological clocks
Jet lag or shift work
Blue light from electronic devices
The above factors can cause sleep disorders. There are several health issues related to irregular circadian rhythms, including diabetes, obesity, depression, bipolar disorder, and seasonal affective disorder.
Fasting and Circadian Rhythm
The brain has evolved to have a variable circadian rhythm, which in the past accounted for changes in light levels and food availability during different seasons. However, in our modern society, this ability to change circadian rhythms has become detrimental.
We are no longer constrained by the day/night cycle. Electricity allows us to have access to light 24 hours a day, which means that people can be awake and hungry at any time of the day.
This then disrupts the circadian rhythm, with frequent eating and eating at night causing changes to the circadian clock. Studies show that night-shift work is associated with lower levels of satiety hormones (the hormones that make you feel full after a meal). In addition, people who were subjected to simulated night-shift work for ten days also developed high blood sugar levels after meals and insulin resistance.
Studies in animals show that fasting and restricting access to high-fat foods to only eight to 12 hours per day helps prevent or reverse metabolic diseases. This has led to the hypothesis that time-restricted feeding (i.e., intermittent fasting) could be beneficial for humans.
Strategies for Incorporating Fasting and Circadian Rhythm Optimization
To avoid the metabolic consequences of having a disrupted sleep/wake cycle and mealtimes that aren’t aligned with the natural rhythms of your body, there are several strategies you can employ. Two such strategies include adjusting your mealtimes and practicing good sleep hygiene.
Meal Timing Considerations
To match your eating times to your sleep/wake cycle, it’s best to eat during the day and fast at night. This is called circadian rhythm fasting, a type of time-restricted eating. It involves eating all your food in the earlier part of the day. There’s no “standard” schedule for circadian rhythm fasting, although it has been suggested that fasting for 12 to 14 hours is ideal.
One important thing to note is that breakfast-skipping is not the best way to achieve a 12 to 14-hour fasting window. Studies show that eating breakfast is associated with better blood sugar, diet quality, and mental health. To learn more about the benefits of breakfast, read our blog post “Breakfast: The Most Important Meal of the Day.”
Therefore, rather than skipping breakfast to extend the fasting window, it’s more beneficial to stop eating earlier in the day (for example, eating dinner at 6:00 pm and then refraining from snacking before bed). This enables you to extend the fasting window to allow for cell repair and immune system regeneration while still reaping the benefits of breakfast and syncing your eating to your body’s natural rhythms.
Sleep Hygiene Practices
In addition to scheduling your meals to align more closely with your body’s sleep/wake cycle, high-quality sleep is also important. To support a healthy circadian rhythm, sleep hygiene is important. Habits that can contribute to a good night’s sleep include:
Going to bed at the same time each night and waking up at the same time each morning.
Keep your bedroom quiet, dark, and at a comfortable temperature.
Avoid using electronic devices such as computers and smartphones for at least two hours before going to bed.
Avoid eating large meals before bed.
Avoid caffeine and alcohol before bed.
Be physically active during the day (this can help you fall asleep more easily in the evening).
Final Thoughts
Research shows numerous benefits of fasting, including activation of cell repair, reductions in inflammation, and improved immune system function. By syncing your mealtimes to your natural circadian rhythm and sleep/wake cycle, you may be able to avoid the negative metabolic consequences of eating large amounts of food at night.
If you’re interested in trying circadian fasting, working with a healthcare practitioner to optimize your mealtimes and meal composition can be beneficial. Click here to book an appointment with Donna Sigmond, an integrative and functional medicine practitioner who can help you explore fasting in a safe and balanced way.