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Chrono-nutrition


Our mealtimes are intimately connected to our physical health
Our mealtimes are intimately connected to our physical health

When I am thinking about how to live well, I often reflect on my cave-dwelling roots. It helps me to consider how did our ancient ancestors live? How did we feed and to rest it to stay alive?


Living outside and in nature, we have evolved physiologically to survive according to the light and dark cycle. Our bodies have evolved to include an in-built clock (and the associated genetics) and our internal clock instructs our 24 hour cycle known as our circadian rhythm.


Our circadian rhythm controls a range of physiological functions such as digestion and metabolism and hormone release. In the early part of the day we are primed to be fed and active and in the late part of the day we are ready to fast, rest and repair. Chrono-nutrition relates to the interaction between when we eat and physiological processes, including metabolism, digestion, and hormone secretion.


Our central clock sits in the brain in an area called the hypothalamus and is influenced by the light-dark cycle through light sensors in our brain. The central clock in turn entrains our sleep wake cycle, autonomic nervous system and melatonin secretion. Local autonomous clocks sitting in our tissues and organs are controlled by the central clock and in turn regulate digestion and glucose homeostasis. Ultimately our clocks are trained to anticipate feeding, fasting, sleeping and waking. When we operate outside our natural circadian rhythm or our body is exposed to light or fed at irregular times the synchrony between the clocks is lost and our physiological processes can become dysfunctional.


Our circadian rhythm can be disrupted by changes in the time we go to bed and wake up ("social jetlag"), meal time alterations, artificial light at night and when we are asleep (including night lights) and movement through time zones. This can often result in changes to digestive regularity and in some cases systemic inflammation.


Circadian misalignment has been associated with weight gain, diabetes, constipation and changes to the microbiome that can cause inflammation, reduced nutrient absorption, digestion and neurotransmitter production.


Disruption of the circadian clock by modern lifestyle factors promotes gut microbiota dysbiosis and inflammation. Source: Touitou Y et al, 2025
Disruption of the circadian clock by modern lifestyle factors promotes gut microbiota dysbiosis and inflammation. Source: Touitou Y et al, 2025

Weight gain can occur when there are disruptions to circadian rhythms that involve shorter or longer sleep and changes to meal timings or energy intake patterns. This happens because our circadian rhythm regulates our hormones and two of the most relevant hormones for body weight are cortisol and insulin. Both cortisol and insulin follow a diurnal pattern, being raised in the morning and lower at night.


The job of insulin is to package away the glucose from our blood following a meal so that it can be used as energy or stored as fat as an energy source for the future. Cortisol stimulates our body to produce glucose in a process called gluco-neogenesis. According to our circadian clock, our insulin response is more sensitive and our energy expenditure is greatest in the early part of the day when the body is expecting to be fed and active and this is therefore when our body is most metabolically efficient.


To compound this, our appetite-regulating hormones are also regulated by our circadian rhythm and these can be disrupted by the same mechanisms, influencing how much we eat and what foods we desire.


Broadly speaking, the more we are awake or feeding during the dark phase, the greater our cortisol, glucose and insulin levels and the slower our metabolic function. This collectively leads to weight gain and can confuse our circadian rhythm, impacting sleep quality.


Key take-away: aligning your food intake with the light/dark cycle and your natural circadian rhythm is a low-cost, and modifiable strategy to help maintain quality sleep, digestive function and reduce the risk of weight gain.


References:

Oike H, Oishi K, Kobori M. Nutrients, Clock Genes, and Chrononutrition. Curr Nutr Rep. 2014 Apr 27;3(3):204-212. doi: 10.1007/s13668-014-0082-6. PMID: 25101217; PMCID: PMC4118017.


Touitou Y, Perlemuter G, Touitou C. Shift work, gut dysbiosis, and circadian misalignment: The combined impact of nighttime light exposure, nutrients, and microbiota rhythmicity. Chronobiol Int. 2025 Aug 7:1-16. doi: 10.1080/07420528.2025.2540039. Epub ahead of print. PMID: 40772701.


Reytor-González C, Simancas-Racines D, Román-Galeano NM, Annunziata G, Galasso M, Zambrano-Villacres R, Verde L, Muscogiuri G, Frias-Toral E, Barrea L. Chrononutrition and Energy Balance: How Meal Timing and Circadian Rhythms Shape Weight Regulation and Metabolic Health. Nutrients. 2025 Jun 27;17(13):2135. doi: 10.3390/nu17132135. PMID: 40647240; PMCID: PMC12252119.




 
 
 

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