There's a good chance you've heard of intermittent fasting (IF). This popular dietary plan emphasizes when you eat during the day by creating scheduled intervals of fasting and eating. Unlike most diets, IF doesn't monitor what foods you eat, only when you eat them. And the health benefits include not only weight loss but increased energy and reduced chronic illness as well.
But what if we could take IF one step further by aligning our meals with our body's internal clock? As it turns out, a different form of intermittent fasting known as circadian rhythm fasting (CRF), or the circadian rhythm diet, can do just that. Before we discuss the benefits of CRF, let's get to know your circadian rhythm in greater detail to find out what it is and how it can improve your health.
What Is the Circadian Rhythm?
The internal clock that dictates wakefulness and sleepfulness is your circadian rhythm. Also referred to as your sleep/wake cycle, it manages how tired or awake you feel during parts of the day.
Your circadian rhythm is controlled by a part of your brain known as the hypothalamus, an area that's sensitive to light. Shine a bright light into your eyes and the hypothalamus sends signals to your brain telling you it's time to wake up.
When it's dark, your hypothalamus instead tells your body that it's time to rest. That's why we naturally wake in the morning with the sun and grow sleepy at night when it sets.
Even though we often think of light versus dark as the only factors that affect our circadian rhythm, eating plays a role too.
The relationship between sleeping and eating is a result of two major hormones: cortisol and melatonin. Secreted from different portions of your brain, cortisol is commonly known as the body's stress hormone that rises in the morning, peaks in the afternoon, and drops at night.
Melatonin, on the other hand, tells your body when it's time to sleep by promoting sleepiness; it's lowest in the morning, but it gradually increases during the day until night when your body winds down. In theory, these hormones work together by helping you feel energized during the day and sleepy at night, thus regulating your sleep/wake cycle.
What Is Circadian Rhythm Fasting?
Also known as the sun cycle diet, circadian rhythm fasting encourages you to time your meals with your sleep/wake cycle and the dips and rises in cortisol. That's because cortisol has an effect on your thyroid hormones, which regulate your metabolic functions and the rate at which calories are burned. When cortisol rises in the morning, your metabolism is locked in to provide your body with energy through the foods you eat. When cortisol falls in the evening, your metabolism slows down to store calories for later use.
Based on this information, it's best to schedule your eating patterns around your body's use of energy. The circadian diet promotes eating during the day when bodily functions are most active, and fasting at night when bodily functions slow down.
But cortisol and metabolism aren't the only factors to consider when establishing a CRF diet. Insulin, a hormone that's secreted by the pancreas, also plays a role. When you eat a meal or snack that contains a lot of carbohydrates, your body responds by releasing insulin to absorb glucose from the bloodstream.
According to the latest research, your body's natural circadian rhythm can be disrupted by this release of insulin if it occurs at night, which may lead to an increased risk of Type 2 diabetes, heart disease, or obesity.
What Are the Benefits of Circadian Rhythm Fasting?
Sticking to an eating schedule that aligns with your sleep/wake cycle and avoids insulin spikes can be incredibly beneficial to your overall health. Let's take a look at some of the benefits that come with CRF.
Perhaps the greatest benefit that occurs as a result of circadian rhythm fasting is weight loss. Fasting allows your body to use energy more efficiently when your metabolism is higher. This reduces the likelihood of weight gain when calories would otherwise be stored as fat. Timing your meals also associates with the thermal effect of food, which describes the amount of energy your body uses to digest a meal.
In fact, one study found that the thermal effect of food is 44% higher in the morning than in the evening. Following the CRF diet can increase the calories your body burns after a meal, which results in a net loss of calories by the end of the day. Remember, if you burn more calories than you consume in a day, you stand a better chance of losing weight.
More Efficient Metabolism
Eating earlier during the day on the circadian diet can also improve your metabolic health and reduce your risk of diabetes. Ongoing research suggests your insulin response is better at the beginning of the day than towards the end. In fact, blood glucose levels are almost twice as high after dinner when compared to breakfast, which supports the idea that you should eat meals earlier when your body is still waking up.
Circadian fasting reinforces your circadian rhythm, which leads to deeper sleep for longer periods of time. Those who practice intermittent fasting also have higher levels of human growth hormone, a hormone that's produced during sleep to repair the body at a cellular level. As a result, those that follow a CRF diet may wake up feeling more refreshed and restored.
Research suggests that the rate at which your digestive system operates is higher at the beginning of the day than at night time. By following a circadian rhythm diet, you stand to improve common digestive problems that might otherwise disturb your circadian rhythm, such as pain, bloating, diarrhea, and constipation.
Strengthened Immune System
One 2020 study found that fasting later in the day, when your melatonin levels are higher, improves B cell recovery. B cells are a form of white blood cell that makes antibodies that act as a signal to your immune system to destroy pathogens like bacteria and viruses.
How Should You Start Circadian Rhythm Fasting?
Follow these tips to begin CRF with success. If you currently take medications or suffer from any metabolic disorders, consider talking with your healthcare provider before establishing any form of fasting diet.
Eat Earlier in the Day
Start by eating your first meal when you wake up, or simply establish an early eating window. Examples of early feeding times include 7 a.m. to 3 p.m., 9 a.m. to 5 p.m., or 5 a.m. to 5 p.m. Consider eating during these windows and fasting outside of them.
Limit Refined Sugars and Grains
Refined sugars and grains are more likely to elevate blood sugar levels after a meal. A diet that consists largely of these foods can lead to insulin sensitivity and insulin resistance over time, which is why you should avoid these foods during mealtime. If you still want to eat foods that are high in carbs, do so earlier in the day when your insulin response won't conflict with your circadian rhythm.
Limit Late-Night Snacking
Snacking or eating meals at night can disrupt your circadian rhythm, which is why it's important to establish strict eating habits based on your preferred fasting windows. Eating late at night can also disrupt melatonin production, making it more difficult to fall asleep.
Follow a Strict Daily Schedule
Strengthen your circadian clock by waking up and going to bed at the same time every day. These habits will help your body understand when it's time to be active versus restful, and bodily systems will adapt in turn.
Focus on Light Exposure
It's important to receive lots of light exposure during the day when your body needs it, as light promotes a series of biological functions that help you stay awake and active. Reduce light exposure at night to help your body understand when it's time to rest and sleep.
Making the Most of the Morning
Your circadian rhythm is designed to regulate sleep and wakefulness, but it also plays a pivotal role in other bodily systems. Your metabolism, digestion, immune system, hormone secretion, and mental wellness stand to benefit from a dialed, strong circadian rhythm as well. Consider timing your meals to align them with your body clock by eating earlier in the day when your metabolism is running at full capacity.
Whether you currently utilize circadian rhythm fasting or not, it’s important that you invest in your health by maintaining a healthy, nutritious diet. Proper food intake can improve your health, boost your metabolism, and increase your longevity. Sign up today for Vital to begin understanding how your diet affects your life and receive personalized recommendations about exercise, food, and daily habits that contribute to a better life.