The interaction between circadian rhythms and nutrition

The circadian system regulates numerous biological processes with roughly a 24-hour cycle, helping the organism adapt to the day-night rhythm. Among others, circadian rhythms regulate metabolism, energy expenditure, and sleep, for which meal timing is an excellent inducer. Evidence has shown that meal timing has a profound impact on health, gene expression, and lifespan. Proper timed feeding in accordance with the natural circadian rhythms of the body might improve metabolic health and reduce chronic disease risk.

Circadian rhythms

Circadian rhythms are controlled by the central clock of the brain, which coordinates biological functions with the light-dark cycle. Along with meal timing, circadian rhythms influence key elements of metabolism such as insulin sensitivity, fat storage, and glucose metabolism. When meal timing is not synchronised with the body's natural rhythm, it can cause circadian misalignment, disrupting metabolic processes and contributing to obesity, diabetes, and cardiovascular diseases.

Literature has indicated that one should eat best during the daytime, particularly synchronised with the active phase of the body. Eating late at night or in the evening when the circadian rhythm of the body is directed towards sleep could impair metabolic function and lead to weight gain, insulin resistance, and numerous other diseases. Also, having larger meals in the morning and smaller meals later in the evening has been linked to improved metabolic health, sleep quality, and even lifespan.

A time-restricted eating window, in which individuals eat all meals within a approximately 10–12 hour window, holds promise for improving human health outcomes like glucose metabolism, inflammation, harmful gene expression, and weight loss (Figure 1).

It is necessary to consider the impact of meal timing on gene expression. Our genes react to a number of stimuli, including environmental cues like food and light exposure. Gene expression of the body's metabolic, immune, and DNA repair processes are regulated by the body's circadian clock. Disturbances in meal timing influence the expression of these genes, which may result in greater susceptibility to diseases and reduced lifespan.

Certain nutrients, such as melatonin in cherries and grapes, and magnesium in leafy greens and nuts, can improve sleep quality and circadian entrainment. Omega-3 fatty acids in fatty fish and flax seeds also have been shown to regulate circadian genes and improve metabolic functions.

Other species

Meal timing is quite varied among species, and animals have adapted such that food-seeking behavior is entrained into circadian rhythm and environmental time cues.

There are nocturnal animals which eat at night, when they are active (Figure 2). These nocturnal animals have evolved to align their meal time with their period of activity to maximise metabolic efficiency and lifespan. Meal timing is optimised in these animals for night activity and digestion.

Humans, and most other animals, are diurnal and consume food during the day. In these animals, consuming most of their calories during the day is conducive to metabolic processes like glucose homeostasis and fat storage. These species tend to have better metabolic health when they are on a feeding regimen that is synchronized with the natural light-dark cycle.

Conclusion

Meal timing is important in human health, genetics, and life expectancy. Synchronising meal times with the body's circadian rhythms optimises metabolic function, reduces chronic disease incidence, and potentially increases longevity by reducing inflammatory genes and upregulating protective ones. This altered gene expression affects the way food is metabolised and metabolic signals are acted upon by the body. Humans naturally gravitate towards eating during daytime hours, while other creatures have feeding habits that are adaptively suited to their own distinct environmental needs. It is important to consider this science and incorporate it into our schedules to receive the best outcome from an activity that we do not normally think about.

Written by B. Esfandyare

Related article: The chronotypes

REFERENCES

Meléndez-Fernández, O.H., Liu, J.A. and Nelson, R.J. (2023). Circadian Rhythms Disrupted by Light at Night and Mistimed Food Intake Alter Hormonal Rhythms and Metabolism. International Journal of Molecular Sciences, [online] 24(4), p.3392. doi:https://doi.org/10.3390/ijms24043392.

Paoli, A., Tinsley, G., Bianco, A. and Moro, T. (2019). The Influence of Meal Frequency and Timing on Health in Humans: The Role of Fasting. Nutrients, [online] 11(4), p.719. Available at: https://www.ncbi.nlm.nih.gov/pubmed/30925707.

Potter, G.D.M., Cade, J.E., Grant, P.J. and Hardie, L.J. (2016). Nutrition and the circadian system. British Journal of Nutrition, [online] 116(3), pp.434–442. doi:https://doi.org/10.1017/s0007114516002117.

St-Onge MP, Ard J, Baskin ML, et al. Meal timing and frequency: implications for obesity prevention. Am J Lifestyle Med. 2017;11(1):7-16.

Patterson RE, Sears DD. Metabolic effects of intermittent fasting. Annu Rev Nutr. 2017;37:371-393.

Zhdanova IV, Wurtman RJ. Melatonin treatment for age-related insomnia. Endocrine. 2012;42(3):1-12.

Prabhat, A., Batra, T. and Kumar, V. (2020). Effects of timed food availability on reproduction and metabolism in zebra finches: Molecular insights into homeostatic adaptation to food-restriction in diurnal vertebrates.Hormones and Behavior, 125, p.104820.