In this modern day and age, our daily lives are “run by the clock,” so to speak. We rely on clocks to keep our lives organized and chugging along on schedule. However, what many do not realize is that the body itself is also run by clocks – circadian clocks, to be exact. Circadian clocks (also referred to as “body clocks”) are collections of genes and proteins that exhibit rhythmic activity, and are located within various tissues and organs in the body. They act as internal “timekeepers,” coordinating important physiological functions such as sleep, hormone release, and metabolism, according to an approximately 24-hour schedule. Together, these clocks produce our circadian rhythm. When factors from our environment throw off the cyclic activities of our body clocks, this disrupts the circadian rhythm. A disrupted circadian rhythm can negatively impact many aspects of health, including blood sugar control. Read on to learn about how circadian rhythm disruption affects your blood sugar, and what you can do to reset your circadian rhythm and thus reverse conditions such as high blood sugar, insulin resistance, stubborn weight gain, and diabetes.
What are body clocks and circadian rhythms?
Before we dive into the details of how circadian rhythm disruption affects metabolic health, let’s cover some of the basics regarding body clocks and circadian rhythms.
As I mentioned briefly before, body clocks are collections of genes and proteins within various tissues and organs that exhibit rhythmic activity over a 24-hour period. The “master” body clock is a structure in the brain called the suprachiasmatic nucleus (SCN). Additional body clocks, called “peripheral body clocks,” are distributed throughout organs such as the liver, pancreas, intestines, and adrenals. The master clock in the SCN regulates the activities of peripheral body clocks, and the peripheral body clocks interact with one another and provide feedback to the master clock. Together, these internal timekeepers coordinate the rhythmic release of various hormones and proteins, and the activation of various cellular receptors, over a 24-hour period. This complex symphony of rhythmic biochemical activity ultimately generates our circadian rhythm.
The circadian rhythm is the body’s internal organization of physiological and biochemical processes that follows an approximately 24-hour cycle and regulates many bodily processes. The circadian rhythm is composed of several different cycles, including the light/dark cycle, sleep/wake cycle, and feeding/fasting cycle. Cues from our environment, such as light exposure, temperature changes, and food intake, influence our body clocks and circadian rhythms. These cues can either help or hinder body clocks, keeping the circadian rhythm in biochemical synchrony or throwing it off-balance.
Examples of factors that disrupt circadian rhythms include:
- Blue light exposure at night
- Lack of bright light exposure during the day (ideally from sunlight)
- Erratic eating habits
- Lack of sleep
- Certain nutrient deficiencies
A disrupted circadian rhythm alters insulin sensitivity
Altered sleep is perhaps the most well-known effect of a disrupted circadian rhythm. However, the effects of circadian rhythm disruption extend far beyond just our sleep habits. In fact, it turns out that the circadian rhythm is also intrinsically linked to blood sugar control. The intricate connection between body clocks, the circadian rhythm, and blood sugar control means that circadian rhythm disruption can lead to disorders such as hyperglycemia, insulin resistance, and diabetes.
A 2017 article published in the journal Obesity Reviews analyzed the research on the relationship between disrupted circadian rhythms and metabolic disorders such as insulin resistance and obesity, and made several fascinating discoveries. The researchers found that body clocks exist in the beta cells of the pancreas, where insulin is made. When the circadian rhythm is working properly (i.e. is “synchronized”), pancreatic beta cells secrete insulin efficiently, thus maintaining tight control of blood sugar levels and minimizing the harmful effects of glucose on the body. When circadian rhythm is disrupted, the pancreatic beta cells do not function efficiently, and this results in inadequate insulin secretion, elevated blood sugar levels, and a higher tendency for glucose to have negative effects on the body (such as causing glycosylation of hemoglobin, producing hemoglobin A1c, a biomarker for diabetes). In addition, this process may also eventually lead to insulin resistance. Therefore, a disrupted circadian rhythm ultimately increases a person’s risk for developing hyperglycemia, insulin resistance, and diabetes (1).
A disrupted circadian rhythm affects leptin signaling
In addition, it was also found that a disrupted circadian rhythm affects leptin signaling. Leptin is a hormone produced by fat cells that is also involved in glucose homeostasis in the body. (2) Leptin is sometimes referred to as the “satiety hormone,” as it helps to regulate energy balance and inhibit hunger. Circadian rhythm disruption makes cells less sensitive to the effects of leptin, causing leptin resistance. (3) Low levels of active leptin (triggered by leptin resistance) disturb blood sugar regulation, and can lead to hyperglycemia. This, in turn, can increase appetite and lead to weight gain.
Light affects blood sugar homeostasis
The light/dark cycle aspect of the circadian rhythm also has a major influence on metabolic health. Evolutionarily speaking, humans are designed to eat during the light cycle and fast during the dark cycle – metabolism of food appears to be most efficient during the (natural, sunlight-driven) light cycle. However, our modern lifestyle filled with artificial light late into the evening hours; this means that we are awake and active long after the natural light cycle has ended. Many people continue to eat well into the night, when they should ideally be asleep and in the fasting. This mismatch of modern-day eating patterns with our evolutionarily-driven circadian rhythms results in overeating, deranged blood sugar, and insulin resistance.
Strategies for re-setting your circadian rhythm to improve blood sugar control
While a disrupted circadian rhythm has many harmful effect on metabolic function, the good news is that there are simple steps you can take to re-set your body clocks, normalize your circadian rhythm, and reverse symptoms of metabolic syndrome. Here are a few ideas:
- Practice time-restricted feeding: A dietary practice called time-restricted feeding has been found to regulate circadian rhythms and improve blood sugar control. Time-restricted feeding refers to eating during a set time frame during the day, such as a period of 10 hours, and avoiding all consumption of food after that period. This practice essentially “syncs” body clocks in your brain, pancreas, and other tissues, normalizing insulin secretion and glucose utilization. In studies using mice, time-restricted feeding has demonstrated the ability to normalize insulin resistance and obesity in the animals.
- Avoid eating late at night. Eating late at night, or close to your allotted bedtime, may impair your body’s blood sugar control. The cascade of hormones released during food intake compete with the production of melatonin, and other cues that are designed to help your body prepare for sleep at night. I suggest that you stop eating at least three hours before bed. (4)
- Avoid blue light exposure at night. Blue light is a short-wavelength light that is emitted from the sun and from technological devices such as digital screens, smart phones, and fluorescent and LED lighting. (5) Blue light exposure during the day from the sun plays a crucial role in maintaining wakefulness and elevating mood. However, blue light exposure at night from electronic devices and artificial light has been found to disrupt blood sugar control. A study published in the scientific journal PLOS One found that people exposed to blue light at night developed elevated blood sugar levels and in insulin resistance. (6) This may be due to the effect of blue light on melatonin production; melatonin is the hormone that induces sleep, and inadequate levels of melatonin have been linked to impaired insulin secretion and abnormal blood sugar regulation. (7)
- Commit to getting 8 hours of sleep. Sleep deprivation has been found to increase levels of ghrelin, a hormone that stimulates appetite and leads to increased food intake. (8) Lack of sleep also has been linked to hyperglycemia and insulin resistance. (9)
A disrupted circadian rhythm significantly impacts your body’s blood sugar homeostasis. Dietary modifications to help manage blood sugar levels and reverse insulin resistance will not be fully effective unless you also re-sync your body clocks so that your circadian rhythm is optimized. By practicing some form of time-restricted feeding, avoiding food consumption late at night, avoiding blue light exposure at night, and committing to getting plenty of sleep every night, you can optimize your circadian rhythm, and thus successfully manage your blood sugar levels and overall metabolic health.