When I hear Circadian Rhythms, I think about patterns, cycles and the 24-hour clock. Then I think about life and a mental tug-of-war usually ensues.

Last week, the 2024 U.S. Olympic Team Trials in swimming wrapped up in what was a landmark event for the sport and arguably amateur athletics as a whole. The Trials were held in Lucas Oil Stadium, home of the NFL’s Indianapolis Colts and a venue first in swim meet history.

USA Swimming reported record-breaking attendance with the meet welcoming more than 285,000 fans. NBC aired live coverage each night of the nine-day event from 8pm to 9pm ET where we saw fan favorites like Katie Ledecky and newcomers like Alex Shackell earn spots on the 2024 U.S. Olympic Team.

Imagine training day in and day out at 5am, 6am or 7am if you are lucky, and then having to step-up, race and perform at your best at 9 o’clock at night in a brightly lit venue on a national stage.

Where is consideration for chronobiology?

Did anyone tell the event organizers about the circadian clock?

Be Ready for Anything

This picture is not unique to sport. Executives get pulled into dinner meetings that last well after dark. Students stay up late and sacrifice sleep to study for exams and meet deadlines. Parents with newborns and infants completely lose sight of their sleep preferences.

People, across all domains, disrupt their natural rhythms for social events and everyday actions as typical as staying up late to watch the end of a movie or see the close of an exciting sporting event in the comfort of their homes on TV. These scenarios are common and don’t even account for the big circadian disruptors like shift work or travel across time zones.

As an athlete, I was taught to be ready for anything. My guess is that the Trials swimmers adapted their training schedules and prepared to compete at night and perform. They did what was required to pursue a thing that they loved. They showed up and gave it their best regardless of the science of the circadian clock.

Chronobiology and Precision Nutrition

In a recent article in Advances in Nutrition, we learn that “elucidating the role of circadian rhythm and chrononutrition” is one of four main research areas identified by the National Heart, Lung, and Blood Institute (NHLBI) as in alignment with precision nutrition and governing strategic visions for health (Pratt et al., 2022).

Precision nutrition is an initiative launched in 2023 by the National Institutes of Health (NIH). It is about personalization, integration and the relationship among the various factors that impact health and disease. These include “genetics and epigenetics, dietary habits and eating patterns, circadian rhythms, health status, socioeconomic and psychosocial characteristics, food environments, physical activity, and the microbiome” (Pratt et al., 2022, p. 1402).

On its face, the goals of the initiative sounds lovely, and a lot like what integrative medicine has been doing for years.

Circadian Rhythms

With regard to circadian biology, the article points to the relationship between feeding behavior, metabolism and the body’s network of circadian clocks. It describes how these “clocks,” which exist in both the brain and peripheral tissues and organs, act as sensors that 1) underlie the mechanisms that motivate eating during certain times of the day, and 2) are affected and commonly disrupted by environmental and behavioral cues (Pratt et al., 2022).

In the context of health and nutrition, what stood out to me was the overarching statement that a “new concept” was emerging. Namely that, “When you eat is equally as important as what you eat, and there are individual differences related to the effects of timing of food intake and health outcomes” (Pratt et al., 2022, p. 1407).

“Modifying the timing of food intake and nutrient composition throughout the day could be a cost-effective intervention to promote healthful dietary and sleep patterns while lowering the risk for adverse health outcomes,” the authors conclude (Pratt et al., 2022, p. 1408).

For me, another tug-of-war in my mind.

Chronobiology 101

To clarify, chronobiology is a branch of science that examines biological rhythms. It looks at the effects of time on internal “clocks” and biological functions (Çalıyurt, 2017). Chronotype is an individual’s preference for wakefulness and activity versus sleeping (ScienceDirect, n.d.).

Circadian rhythms are embedded within the science of chronobiology and refer to the body’s natural daily patterns that, importantly, are endogenously generated and move or oscillate around a 24-hour clock (Kuhlman et al., 2018).

Under normal circumstances, these endogenous oscillations are synchronized to the environment, and it is generally thought that biological clocks provide an adaptive advantage by ensuring that an organism’s internal biochemical and physiological processes, in addition to behavior, are optimally adapted to the local environment, explain Kuhlman et al. (2018, p. 1) in Introduction to Chronobiology.

The important learning related to health and disease is that evidence is increasingly showing that disruptions to circadian rhythms are having negative consequences for health. These include poor sleep and corresponding drowsiness and safety issues, decreased immunity, heightened cancer risk and increased risk of cardiovascular and metabolic disease (Kuhlman et al., 2018).

What causes disruptions? Artificial light, travel, professional and social engagements out of synch with the natural cycles of daylight. In other words, aspects of reality all linked to those everyday instances mentioned earlier and deeply-rooted in modern life.

Chrononutrition and Conflict

To bring it back to precision nutrition, chrononutrition and the NHLBI, we need to understand that chrononutrition is essentially a discipline within chronobiology that is looking to leverage what we know about nutrient metabolism with what we know about circadian rhythms to yield better outcomes for health.

For example, we know that eating before bed can have adverse effects on glucose regulation—how the body processes sugar—and that evidence is showing that this may contribute to obesity and obesity-related disease (Pratt et al., 2022). An intervention or health guideline based on chrononutrition would therefore advise against eating into the evening hours or at night.

Ultimately, in practice, the argument is this: “Modifying the timing of food intake and nutrient composition throughout the day could be a cost-effective intervention to promote healthful dietary and sleep patterns while lowering the risk of adverse health outcomes” (Pratt et al., 2022, p. 1408).

My questions are:

Will chrononutrition create a new wave of trendy advice and confusion?

Will it move us farther away from the big rocks and levers like energy balance, nutrient intake and mitigating the impact of chemicals on health?

Will it yield an abundance of unrealistic considerations and impractical advice?

Thoughts on Application

Bouncing back to the sports realm, I have encountered a mix of interesting insight. Dr. Marc Bubbs, as one case, offers useful tips for caffeine intake, alcohol, blue light and managing jet lag to optimize sleep and support the circadian clock.

Other evidence-based literature, however, has yielded more questionable results.

For example, a 2021 review article looking at circadian rhythms and sports performance concluded that, “Training sessions should be planned according to the optimal time of day for each athlete. It’s essential to take into account individual chronotype. The desynchronization of circadian rhythms can cause a decrease in physical performance” (Ayala et al., 2021, p. 1).

Share that with any coach or team sport athlete and my guess is they’ll laugh.

An Expanded Perspective

When we re-widen the lens, expand our thinking and focus on the immediate need to change human health, here is where I end up.

First

Chrononutrition is ultimately about personalization. If carefully managed and used in conjunction with what we know to be true for good health, chrononutrition can be additive in treatment of disease and interventions. Prioritizing when we eat, however, cannot replace prioritizing what we eat. For chrononutrition to be effective, the “when” cannot replace the “what.” They must be considered in tandem.

Second

From a coaching perspective, chrononutrition and circadian biology could create more entry points for client motivation and connection. This is a big win. Options is one of the four pillars of the GROW coaching framework, which includes Goals, Reality, Options and Will.

The art of coaching includes helping clients find meaningful options for action—options that resonate and elicit heightened willingness and motivation to execute new behaviors and change. Circadian science has the ability to influence and add to this realm.

Lastly

The science is full of unique and meaningful nuggets. When optimization is part of the goal, it is the attention to detail and key nuggets that often separate the good from the great. When health and wellbeing are at the forefront, the nuggets could be the impetus for momentum or change.

I stand as one case in point. I love a snack before bedtime. It has been part of my eating routine for as long as I can remember and, despite the sleep science wisdom that cautions against eating before bed, I have never felt a drive or desire to change.

In researching for this article, I learned that the body’s master clock in the brain says, “time for bed” at night. When we eat during this bedtime window, the body’s liver clock (that’s one of the peripheral organ-specific clocks) says, “I need to process this food.” The two essentially enter a conflict (this is called circadian misalignment), which can have long-term implications for health (Wells, 2023).

Fascinating. And, more to the point, substance that for the first time in my 41 years has elicited a true desire to change my habit of having a snack before bed.

What is your nugget of circadian wisdom? What aspects of chronobiology could support your clients or you? How can you use circadian science to increase performance or realize your vision of health?

Thank you for reading, my friends! Wishing you good health and joy on this July 4th weekend! Reach out with questions or comments anytime.

References

Ayala, V., Martínez-Bebia, M., Latorre, J. A., Gimenez-Blasi, N., Jimenez-Casquet, M. J., Conde-Pipo, J., Bach-Faig, A., & Mariscal-Arcas, M. (2021). Influence of circadian rhythms on sports performance. Chronobiology international, 38(11), 1522–1536. https://doi-org.pacificcollege.idm.oclc.org/10.1080/07420528.2021.1933003

Çalıyurt O. (2017). Role of Chronobiology as a Transdisciplinary Field of Research: Its Applications in Treating Mood Disorders. Balkan medical journal, 34(6), 514–521. https://doi.org/10.4274/balkanmedj.2017.1280

Kuhlman, S. J., Craig, L. M., & Duffy, J. F. (2018). Introduction to Chronobiology. Cold Spring Harbor perspectives in biology, 10(9), a033613. https://doi.org/10.1101/cshperspect.a033613

Pratt, C. A., Brown, A. G. M., Dixit, S., Farmer, N., Natarajan, A., Boyington, J., Shi, S., Lu, Q., & Cotton, P. (2022). Perspectives: on Precision Nutrition Research in Heart, Lung, and Blood Diseases and Sleep Disorders. Advances in nutrition (Bethesda, Md.), 13(5), 1402–1414. https://doi-org.pacificcollege.idm.oclc.org/10.1093/advances/nmac053

ScienceDirect. (n.d.). Chronobiology. Retrieved June 25, 2024, from https://www.sciencedirect.com/topics/neuroscience/chronobiology

Wells, K. (Host). (2023, August 7). The Importance of Circadian Rhythm and Why Biological Timing Is Everything With Alex Dimitrov (No. 681) [Audio podcast episode]. In The Wellness Mama Podcast. https://wellnessmama.com/podcast/681/