Circadian Rhythm
What is it and why does it matter?
Your circadian rhythm is your sleep-wake pattern over the course of a 24-hour day.
It helps control your daily schedule for sleep and wakefulness. Most living things have one. Circadian rhythm is influenced by light and dark, as well as other factors. Your brain receives signals based on your environment and activates certain hormones, alters your body temperature, and regulates your metabolism to keep you alert or draw you to sleep.
Living a healthy, active lifestyle that promotes proper rest will help you maintain this important component of your body.
Some may experience disruptions to their circadian rhythm because of external factors or sleep disorders. Maintaining healthy habits can help you respond better to this natural rhythm of your body.
How is circadian rhythm related to overall health?
Maintaining your circadian rhythm is vital to your health. If you experience a disruption to your circadian rhythm and struggle to get the proper amount of sleep, you can experience both short-term and long-term effects to your health.
Disruption to your circadian rhythm can cause health conditions in several parts of the body in the long term. This includes your:
organs
cardiovascular system
metabolism
gastrointestinal system
skin
You may also be more susceptible to diabetes, obesity, and mental health conditions.
Short-term disruptions to your circadian rhythm may result in:
memory issues
lack of energy
delayed wound healing
changes to your hormone cycle that may impact fertility
problems with your digestion and bowels
shifts in your body temperature
Circadian rhythm and weight
If food is ingested outside of typical mealtimes, then the subsequent release of insulin also occurs outside of a typical schedule.
As a result of this, the circadian rhythm can be disturbed, affecting both weight loss and weight gain.
How does this work?
Cortisol, the stress hormone, typically peaks at 8 am, allowing individuals to wake from sleep, and falling to its lowest concentration at 3 am. This rise also occurs in line with exposure to sunlight. By noon, cortisol levels begin to fall inverse to serotonin and adrenaline, which elevates mood and energy.
The increase in energy levels, in particular, stimulates feelings of hunger and prompts the person to eat. Throughout the rest of the day, cortisol levels continue to decline, and serotonin is synthesized into melatonin, promoting feelings of sleepiness. Alongside this is a decrease in blood sugar levels, which drop to their lowest point at 3 am. This balance can be disturbed in those that snack late at night or eat meals outside typical times, affecting stress levels and digestion.
Circadian Fasting
In a nutshell, circadian fasting means aligning your eating with the body’s natural circadian rhythms — aka, being active during the day and resting at night. In terms of food, that means not eating from evening until morning.
Circadian fasting means limiting your eating to daytime hours, with a fast between dinner and breakfast. It is based on the idea that up until very recently, people didn’t have a lot of late-night eating options, so our bodies are optimized to eat and digest during the middle and earlier parts of the day.
A broad body of research has consistently found powerful benefits of circadian fasting. The studies show benefits including less chronic disease (like diabetes, high blood pressure, and obesity), improved longevity, and even a protective effect against cancer, among others.
A fasting diet for women can be particularly beneficial, because of the threefold benefits to hormone health, gut health, and immune health.
It generally takes at least 12 hours to begin seeing the benefits of fasting. At this point, your body has worked through the stored sugar in your blood and liver, and begins using fatty acids for fuel. This switch from sugar to fatty acids — and then back to sugar when you break your fast — is what turns on certain genetic processes that improve the resilience of cells.
When determining your eating window, remember that it should be 12 hours or shorter, and include your peak digestion time, which is from noon to 5 P.M.
You don’t need to use the same circadian fasting schedule every day to get benefits. You can fast for 12 hours on certain days, 16 hours on other days, and even skip days.
In summary, supporting your circadian rhythms can help improve overall health including mood, sleep, and weight. Getting sunlight first thing in the morning to trigger the rhythm, keeping a 12 hour window between your last meal and first meal the following day and limiting eating after sundown, can all help improve your rhythm.