Synchronizing gut health and metabolism with the circadian rhythm

In this project, I am going to be exploring the role the circadian rhythm, and how disruptions in it can lead to health problems in the gut, which would then affect the metabolic function.
Arnav Sharma
Grade 11

Presentation

No video provided

Problem

 

People today have irregular sleeping and eating schedules due to work, travelling or lifestyle choices. Disruptions in such factors can cause an internal body clock known as the circadian rhythm to malfunction and lead to imbalances in the gut bateria. Gut plays a significan role in digestion and metabolism and disturbances can impact on how the body absorbs and processes nutrients, and regulates hormones. If disruptions are to be continued they can lead to adverse consequences such as health risks like diabetes. I will be talking about the role of the circadian rhythm and how disrupting it can cause adverse affects to the gut microbiota, and how that can lead to metabolic malfunction. The goal of this study is to piece everything together through exploring microbial composition, metabolic hormones and gut bacteria. Hopefully by the end of this study, readers can find themselves at a better position of understanding things that are influential.

 

 

Method

In order to understand this the science behind the circadian rhythm along with how it connects to different tasks of the human body, it is crucial to have some prior knowledge on the matter. Below I have listed they way I will be moving forward with this topic, in various questions/themes which will towards the end give light to my hypothesis. This following order will give readers a chance to comprehend basic information beforehand, as well as throughout the entirety of the project.

 

  • Introduction  
    • What is the Circadian Rhythm? How does it work/what part of the brain controls it?  
    • The 24-hour cycle on gut bacteria 
    • Metabolic Hormones
  • Circadian rhythm and gut health
    • Sleeping behaviours 
    • Gut diseases that correlate to sleep disruptions 
    • Types of gut bacteria most sensitive to the circadian rhythm.
  • Body's clock on the metabolic function
    • Impacts of the rhythm on metabolism controlling hormones 
    • Disrupted gut bacteria leads to metabolic disorders?
    • Role of factors such as jet lag and metabolic imbalances?
  • Maintaining a good circadian rhythm help with gut health + metabolism?
    • Consistent meal/sleep schedules improve gut microbiota
    • Role of probiotics agaisnt circadian rhythm disruptions

 

Hypothesis: Disruptions in the circadian rhythm in the human body, is the cause of negatively affecting the gut microbiota, which in turn influences the metabolic function, thus impacting the ability to absorb nutrients. 

Research

 

What is the Circadian Rhythm? 

The circadian rhythm is a 24-hour clock inside living organisms which consists of different releases such as hormone release or sleep schedules/body temperature that are influenced by various factors. Basically the circadian rhythm is an in-built natural clock in humans which makes us aware of what to do, through the help of signals in the body that partake at certain periods of time. Different body parts contain different 
To understand the science behind this, it is important to understand what body parts are key in this natural system. [1]The primary body parts that are directly linked into regulating the circadian rhythm are the Suprachiasmatic Nucleus (SCN) (figure 1), the Pineal Gland (figure 1), as well as the peripheral clocks all found in the brain. The Suprachiasmatic Nucleus contains a set of neurons which are located inside the hypothalamus in the brain which receives light cues from the body to maintain the circadian environment. On the other hand, the [2]pineal gland, also located in the brain, produces melatonin; the main hormone involved in the sleep-wake cycle. 
 
Figure 1: Illustration of the SCN and Pineal Gland inside brain
 
 

How does it work/what parts of the brain controls it? 

The mechanism begins when [1]axons from the retinal ganglion cells detect a transition from a lighter environment (during the day) to a less lit environment (towards the evening/night). Both timings contain different processes which lead to either inducing or preventing sleepiness. 
[1]In the daytime, these retinal ganglion cells found inside the eyes send signals from the optic nerve (cranial nerve 2) to the SCN. The SCN then inhibits another signal to the paraventricular nucleus (PVN) using a neurotransmitter known as gamma-amino-butyric-acid (GABA). This neurotransmitter is the reason why melatonin is not released during the day, keeping the body attentive. On the other hand when the sun begins to set, and less light is being penetrated through the eyes, it causes the retinal ganglion cells to reduce their stimulation to the SCN which activates the PVN. The PVN then signals the intermediolateral nucleus (IML) to the superior cervical ganglion which induces sleepiness as melatonin in the body becomes active. In short, during the day the SCN abolishes melatonin production while during the night it makes use of it.

 
 
 

How do gut bacteria follow a 24-hour cycle?

Gut bacteria follow a 24-hour cycle known as the daily oscillation in which they are primarily dependent on food intake and meal timings, which influence the bacteria's activity. Certain bacteria are more abundant during specific times during the day and some are less abundant in the night. For instance, in 2014 a few researchers concluded that commensal genes known as Lactobacillus thrives during the active phase, in which energy harvest, DNA repair, and cell growth's functionality is elevated within the microbiome. This bacteria contributes to the majority of carbohydrate digestion which is only possible during times in which energy levels are at its peak. Similarly, in the resting phase, Bacteroides assist in processes such as detoxification. This occurs during this period of time because the body is not actively consuming or digesting their food, which allows the microbiota to change its prime concern. Thus, gut microbiota align themselves to the circadian rhythm of a person which signals them to adjust/fluctuate their activity based on the body's internal clock.
 
 
 

What role do metabolic hormones (e.g., insulin, melatonin) play in linking circadian rhythm to digestion?

Hormones like insulin and melatonin are metabolic hormones that link the circadian rhythm with digestion by controlling energy balances, glucose metabolism and the signals from the hunger sensor. The blood sugar controlling hormone insulin is secreted more during the day when the body is producing more of it. It means that the body would best know how to deal with blood sugar if we eat during the day. However, melatonin is a hormone that controls sleep and is responsible for preventing glucose spikes by blocking insulin release. There are still drawbacks to eating at night, including poor glucose metabolism.  
 
 
 

Sleeping Behaviors and Gut Microbiota Diversity:

As earlier stated, gut microbiota fluctuate based on certain conditions. The bacterial population varies in composition as well as function throughout the day. Any changes in the microbial rhythms can lead to disruptions in sleep patterns such as sleep deprivation. Moreover, sleep deprivation can lead to several problems such as irregular eating patterns and hormonal fluctuations. These disturbances can activate the gut-brain axis, in which the gut communicates to the brain and dysfunction through various steps. Below is a step-by-step breakdown of how the interaction works:
 
  1. Food and microbiota interaction
    1. The food that’s been consumed, gets broken down through substances such as short-chain fatty acids (SCFAs) (e.g. acetate)
  2. Gut signals enter the brain
    1. Vagus Nerve: Known as the “superhighway” for signals, which connects the gut to the brainstem. Gut bacteria can signal the nerve based on factors such as mood or stress.
    2. Immune System: Cytokine molecules are produced as the gut bacteria influences the immune cells. If the gut is imbalanced then it can result in inflammation which increases the risk of neurodegenerative diseases such as depression.
  3. Microbial Metabolites
    1. Once the gut bacteria have produced SCFAs they can travel through the bloodstream to reach the brain.
    2. The SCFAs can also help produce neurotransmitters that assist to uplift mood, sleep, behaviour such as dopamine and serotonin (5-HT)
Endocrine signalling (special gut cells only), can release hormones such as cholecystokinin (CCK) which can affect sleep. 

 
Key communication pathways of the microbiota–gut–brain axis. There are numerous mechanisms through which the bacterial commensals in our gut can signal to the brain. These include activation of the vagus nerve, production of immune mediators and microbial metabolites (i.e. short-chain fatty acids [SCFAs]), and enteroendocrine cell signalling. Through these routes of communication, the microbiota–gut–brain axis controls central physiological processes, such as neurotransmission, neurogenesis, neuroinflammation and neuroendocrine signalling. Dysregulation of the gut microbiota subsequently leads to alterations in all of these central processes. There have been numerous reports of alterations in the gut microbiota in neuropsychiatric conditions, which may account for the behavioural abnormalities that are characteristic of these conditions. Normalizing the composition of the gut microbiota with use of probiotics and prebiotics may represent a viable treatment option for neuropsychiatric conditions. 5-HT serotonin, CCK cholecystokinin, GABA γ-aminobutyric acid, GLP glucagon-like peptide, IL interleukin, PYY peptide YY, TNF tumour necrosis factor
Figure 2: Animation showing gut-brain axis function
 

An imbalance in this system could result in a living organism getting diseases such as dysbiosis, which is an imbalance in the gut microbiota. Overtime the gut-brain communication can cause further harms to the body such as neuropsychiatric disorders.

 
 
 

Gut diseases that correlate to sleep disruptions:

[3]Gut-related issues, such as irritable bowel syndrome (IBS) are closely related to sleep problems. This is because of the gut-brain axis, which is a communication network that allows the gastrointestinal tract and the central nervous system to exchange signals. [4]A small study analyzed by a team of researchers in 2021 used survey data from the National Comorbidity Survey-Replication (NCS-R) which examined how often sleep issues appeared with U.S adults who have IBS. They concluded the relationship between proving that people who have IBS often experience sleeping disorders moreover, irregular circadian rhythms.
 
  • 3.1 times as likely to have symptoms of insomnia
  • 4.6 times as likely to have symptoms of hypersomnia(excessive sleepiness)
  • 5 times as likely to have symptoms of both insomnia and hypersomnia 
Not only that, a larger research done by researchers at [5]PubMed in 2018 used a total of 63,000 participants in order to conclude that 37.6% of people with IBS are already facing a sleep disorder of some kind. 
 
 
 

Types of gut bacteria most sensitive to the circadian rhythm:

If the normal cycle of bacterial growth and activity is upset then irregular sleep patterns can have a detrimental effect on the diversity of the gut microbes. [3] Dangerous bacteria such as the Clostridium and Enterobacteriaceae cause disruptions in metabolism along with gut inflammation. On the other hand, some beneficial probiotic bacterias such as the Lactobacillus and Bifidobacterium can flourish in a stable circadian rhythm. Furthermore, sleep deprivation can raise stress hormone cortisol levels which can later unstabilize the gut microbiota since it introduces the growth of harmful bacteria. These imbalances can result in problems such as type 2 diabetes, and increased gut permeability, and ailments like irritable bowel syndrome (IBS). 

 
 
 

Circadian rhythm's impact on metabolic function

Not only does the circadian rhythm influence gut health, it plays a vital role in maintaining a healthy metabolic function through regulating hormone release, digestion and energy storage. There is a diurnal cycle which is really important for metabolic hormones such as insulin, ghrelin, and leptin. Consumption of insulin in the daytime is highly sensitive and it suggests that eating with the exposure of natural light promotes improved glucose metabolism. The hormone that controls hunger is ghrelin which peaks before meals and happens simultaneously with sleep-wake cycles. These hormones, if they are to get imbalanced by the circadian rhythm disruptions can raise the risk of type 2 diabetes and obesity.
 
 

Disrupted gut bacteria contribute to metabolic disorders?

Disruptions in the gut microbiota have been directly linked to metabolic disorders such as obesity. According to several researchers, microbiota affect fat storage as well as glucose metabolism. This was proven from an [7]experiment that took place where germ-free mice, who do not contain gut bacteria were examined and were found to have resisted obesity as well as metabolic dysfunctions. Moreover, the gut bacteria from the obese mice were transplanted inside of the germ-free mice which led to an increase in their fat as well as insulin resistance, emphasizing the direct connection between gut microbiota and metabolic health. 
 

 

Role of Factors Such as Jet Lag and Metabolic Imbalances

Disruptions of the circadian rhythm, which are caused by jet lag can contribute to several metabolic imbalances, such as less energy being used for breaking down food, blood sugar levels and digestion [Fg. 2]. For instance, an experiment conducted by [8]several researchers from University of Surrey and the University of Aberdeen, made participants delay their mealtimes and sleeptimes by 5-hours in means of a jet lag stimulation. They found out that the participants had shifted their meal and sleeptimes 5 hours later than they used to as usual. The researchers then measured bodily functions such as energy expenditure, blood sugar levels, gastric emptying rate as well as alertness levels within the participants. They then identified a few key findings being that metabolic effects would recover after 2-3 days and that the body's clock and sleepiness levels took even longer to recover (more than 5 days). The following experiment suggested that both the circadian rhythm and metabolism were impacted from being in a jetlag. Furthermore, they concluded that the master clock took longer to reset (feelings such as alertness), and on the other hand metabolism effect being temporary and dependent on the circadian rhythm.

 
 
New study investigates how jet lag can disrupt metabolism
Figure 3: Illustration of effects in human body after 5-hour delay
 
 
 

Consistent meal/sleep schedules improve gut microbiota:

It is true that having a consistent meal and sleep schedules can lead to a healthier gut microbiota, however, to a certain extent. A body is required to carry various types of micronutrients in order to support such complex functions that take place inside places like the gut. Meaning, a healthy meal schedule is required along with it being consistent in order to better support sleep timings which then in turn increases gut microbiota diversity. Foods that are rich in fiber influence the development of good gut bacteria as they synthesize short chain fatty-acids (SCFA), whole foods that are high in fats or sugar can lead to negative consequences for microbial balance. The use of prebiotics and probiotics also alter microbial communities. Sleep disturbances such as irregular sleep or insomnia, can have adverse effects on the gut microbiota and can upset the circadian rhythm. Such effects can arise from gut-brain dysregulation, which in turns brings changes to microbial diversity and also plays a role in metabolic disorders. This dysregulation is a disruption between the interaction of the gut microbiota and brain. 
 
 
 
Figure 4: "Variables that affect the human gut microbiota." 
 
Changing habits such as avoiding disturbances that impact sleep and mealtimes can modify the composition of gut microbiota. Prompting to eating foods that are critical for the gut such as whole grains and proteins can significantly aid in maintaining a healthy gut, and creating sleep schedules based on how your body performs with what amount of sleep and when can also improve the gastrointestinal (GI) system, and thus the microbiota.
 
 
 

How probiotics help fight against poor circadian rhythm

Certain dietary measures can help alleviate circadian rhythm disturbances. Kefir and yogurt are fermented foods that contain probiotics, which are beneficial for the equilibrium of intestinal microbes. [9]Dairy products such as yogurt are known to be rich in tryptophan (Trp), which is an amino acid that has great melatonin production capacity. As earlier mentioned, micronutrients can be highly beneficial to support complex functions and promote sleep, and yogurt is significantly high in them. 

 

 

 

Data

Conclusion

In this project, I studied the impact of circadian rhythm disruptions on the gut microbiota and how it, subsequently, impacts metabolic function and nutrient absorption. When sleeping and eating are out of sync, there is disturbance in the gut bacteria, which can negatively impact metabolic hormones like insulin, melatonin, and ghrelin. This in turn lead to problems such as indigestion, tiredness, and in the worst possible situation, long term health issues like obesity and diabetes. This study gave insight on factors that could disupt the circadian rhyhm, and in return what those disruptions can do to gut health and the metabolic function. 

 

 

Source of Error: I will improve on citing every information that is found on sources as some links are hard to locate after you have done writing. I will do this through keeping my citations in the text before I start my writing. Future research can include looking at different lifestyles and choices that would promote disruptions in the circadian rhythm, through exploring different bacterias and metabolic hormones.

Citations

Bass J, Takahashi JS. Circadian rhythms: Redox redux. Nature. 2011 Jan 27;469(7331):476-8. [PMC free article] [PubMed] [Reference list]

Arendt J, Aulinas A. Physiology of the Pineal Gland and Melatonin. [Updated 2022 Oct 30]. In: Feingold KR, Anawalt B, Blackman MR, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK550972/

Pineal gland | HealthLink BC. (n.d.). https://www.healthlinkbc.ca/healthwise/pineal-gland

Wikipedia contributors. (2025, March 3). Suprachiasmatic nucleus. Wikipedia. https://en.wikipedia.org/wiki/Suprachiasmatic_nucleus]

Swaim, E. (2025, February 19). How IBS can disrupt your sleep, plus tips to get a better night’s rest. Healthline. https://www.healthline.com/health/ibs/ibs-and-sleep#other-conditions

Duan, L., Wang, B., & Duan, R. (2018). Prevalence of sleep disorder in irritable bowel syndrome: A systematic review with meta-analysis. Saudi Journal of Gastroenterology, 24(3), 141. https://doi.org/10.4103/sjg.sjg_603_17

Boulangé, C. L., Neves, A. L., Chilloux, J., Nicholson, J. K., & Dumas, M. (2016). Impact of the gut microbiota on inflammation, obesity, and metabolic disease. Genome Medicine, 8(1). https://doi.org/10.1186/s13073-016-0303-2

Backhed F, Ley RE, Sonnenburg JL, Peterson DA, Gordon JI. Host-bacterial mutualism in the human intestine. Science. 2005;307:1915–1920. doi: 10.1126/science.1104816. [DOI] [PubMed] [Google Scholar]

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University of Surrey. (2024, November 19). How jetlag can disrupt our metabolism. ScienceDaily. https://www.sciencedaily.com/releases/2024/11/241119132709.htm

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Additional Links:

https://www.ncbi.nlm.nih.gov/books/NBK519507/#:~:text=Circadian%20rhythm%20is%20the%2024,Earth's%20rotation%20around%20its%20axis.

https://my.clevelandclinic.org/health/articles/circadian-rhythm#:~:text=What%20is%20circadian%20rhythm?,hormones%2C%20digestion%20and%20body%20temperature.

https://www.healthline.com/health/healthy-sleep/circadian-rhythm#:~:text=Your%20circadian%20rhythm%20is%20your%20body's%20natural%20way%20of%20keeping,reviewed%20on%20January%2022%2C%202025

https://www.sciencedirect.com/topics/immunology-and-microbiology/circadian-rhythm#:~:text=Circadian%20rhythms%20are%20cycles%20of,temperature%20that%20pervade%20the%20biosphere.

https://www.uclahealth.org/medical-services/sleep-medicine/patient-resources/patient-education/circadian-rhythms#:~:text=Circadian%20rhythms%20are%20regulated%20by,other%20parts%20of%20the%20brain.

 

 

 

 

 

 

Acknowledgement

I'd like to acknoledge Ms. Trainor for supporting and helping me throughout this project. Thanks Western Canada High School for giving me the oppurtunity to participate in this. Also would like to thank CYSF and UCalgary for organizing this wonderful fair for students like me.