How to Eat in Harmony with Your Circadian Rhythms

Once again, cutting-edge Western science is consistent with what Ayurvedic wisdom has been teaching all along. A recent review study reveals that, when it comes to the timing of meals, genetics and nutritional science are reading from the book of Ayurveda.

The study by researchers at University of Illinois, published in Nutrition Reviews, looked at the relationships between circadian rhythms, eating behaviors, and the trillions of bacteria in our lower gastrointestinal (GI) tract, called the microbiota.

Our brain, gut, and microbiota communicate with each other in a complex three-way conversation, moment by moment through the day. While scientists are still puzzling out the detailed code of the conversation between these integrated aspects of the whole, Ayurveda offers guidelines for staying in balance.

Circadian Rhythms

The rotation of the earth in relation to the sun creates 24-hour light and dark cycles that have been shown to impact human health in more complex ways than previously understood. Circadian rhythms have been shown to affect gene expression, metabolism (the complex physical and chemical reactions that support life), and a host of functions that play into nutritional and overall well-being—including how the liver handles fat, cardiovascular function, weight, and blood sugar regulation.

Western clinical science is just beginning to look at how circadian rhythms influence nutrition, but Ayurveda has long held that when and how we eat is at least as important as what we eat. This newly integrated body of science might help explain why it’s beneficial to eat our largest meal at midday—an Ayurvedic guideline for eating in balance with nature. 

Microbiota Rhythms

Health is intimately tied to the microbiota. Its state impacts your immune system (how your body handles infections and injuries); metabolic system (how your body uses food and operates overall); neurological system; and digestive well-being. A range of life choices also impact the microbiota, including food choices, drugs and supplements, sleep, disease, stress, your environment, and, as it turns out, the time of day when you eat and your “eating window” (the time between your first and last eating events of the day).

Researchers have found that the microbiota is diurnal, meaning that it is more active in the daytime than at night. Our brains and body are diurnal, too. There are internal light meters in the human brain, and in clock proteins in nearly every cell. The sleep-wake cycles guided by the light and dark hours of the day interact with the central nervous system and the pituitary gland to exert effects on the endocrine (hormonal) and other systems.

Getting Back in Balance

Historically, we have eaten during the day, and fasted at night. However, with the advent of artificial light, we no longer eat in accord to natural rhythms of the day, but whenever is convenient. Dietary intake misaligned with the circadian clock has been shown to negatively impact human health; for example, a study published in 2018 showed that night-shift workers have a 43 percent increased risk for obesity.

Regardless of the modern environments we create that enable us to operate independent of the limits of nature, deep inside each and every cell in our bodies, we are intimately tied to those rhythms. I’m not suggesting that we avoid artificial light, but rather that we bring awareness to its possible destabilizing effect, understand the nourishing qualities of natural light and rhythms, and take time to reorient to natural light, natural sleep-wake cycles, and natural eating/fasting cycles.

Here are few tips to reconnect your eating routines with the natural flow of nature and life.

  1. Eat your main meal during daylight hours—at lunch, if possible. Avoid heavy meals very late or very early in the day.
  2. Consider reducing your “eating window”—the number of hours between your first and last meal of the day. Some early studies suggest that when we reduce that window from 14 hours to 10 or even less, there is metabolic benefit. You might try this as an experiment.
  3. Research has shown benefits from both reducing and increasing meal frequency—the number of times we eat through the day—which likely means that the benefit is individual: Some people do better eating more often, others do better with fewer meals or snacks through the day. Ayurveda recommends not eating between meals in order to keep the agni (digestive fire) strong. See what works for you.
  4. Take time to reorient to circadian eating after travel or a period of working well beyond nature’s light and dark cycles. This is particularly important in the colder, darker seasons, when flu bugs are common.

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Annie B. Kay, MS, RDN, E-RYT 500, C-IAYT, is an author, nutritionist, Kripalu faculty member, and important voice in whole-foods nutrition and yoga.

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