Circadian Nutrition: The Science of Eating at the Right Time

Everyone has heard the saying "breakfast is the most important meal of the day," and there is truth behind it. In fact, people who regularly skip breakfast are 21% more likely to suffer from a cardiovascular disease event (Ofori-Asenso et al., 2019). Meal-skipping has become more prominent over the last 40 years, as the average person has become increasingly busier. There has been a transition away from 3 set meals a day to snacking and varied mealtimes (Kant and Graubard, 2016). Additionally, when trying to improve health through food, few pay attention to or reduce unhealthy food habits related to the timing of meals. Instead, many focus solely on the content of their meals. Bad meal timing, specifically a schedule that isn’t matched to a person’s circadian rhythm, has surprisingly many consequences. This article explores why and how eating at the ‘wrong’ time impacts health, and how to reduce this impact.

(Ferreira, 2019)

Circadian Eating Rhythm

What determines when the body is best primed to eat? It’s the body’s internal clock, the circadian rhythm, which determines sleep-cycles, hormone regulation, and digestion. A person’s unique circadian clock is determined by their exposure to light, which could be the sun or artificial light. When someone stays up late or wakes up early in the morning, their circadian clock is not aligned with light and will adjust over time. Timing of meals is so important, because all digestive organs have their own internal clocks, working more efficiently during the day, peaking on average around noon, and slowing down into the night. Additionally, the hormones released throughout the day, like insulin, ghrelin, and leptin, which manage sugar levels, hunger, and fullness, are all regulated by the circadian rhythm ("Circadian Rhythm", 2024) The body prepares itself to eat during a certain period during the day and disrupting its natural timeline means the body undergoes increased strain during the digestive process. 

(Smith, 2016)

When Should You Eat?

Generally, eating during the day while the body is naturally ready for it is considered the healthiest. However, there are still many meal timing structures that one can use depending on their goals. One of the most popular of these is time restricted eating or intermittent fasting. There are many variations of these including eating all meals in an early 8 hour window, restricting calorie intake 2 of the 7 days of the week, alternate day fasting, etc. (Snyder, 2023). These methods have been extremely successful in weight-loss, as the body has a higher metabolism and is more insulin-sensitive in the morning and afternoon so less fat is stored, blood sugar levels are controlled, and energy usage of food is more efficient. (Lee et al., 2024). Also, as all these eating patterns focus on eating earlier in the day, the digestive system does not need to work during the night and sleep quality is improved.

Key Takeaways

The human body is built to eat meals at certain time periods throughout the day based on its circadian rhythm. The exact time of meals depends from person to person and it can be optimized by experimenting with different meal timings and seeing what feels the best. Although eating a late-night meal or skipping breakfast once won’t permanently damage you, doing so over a period of months and years will increase the risk of metabolic and cardiovascular diseases. Next time you’re planning a meal, remember it's not just what you eat that matters, but also when you eat it.

References

1. Circadian Rhythm. (2024). Cleveland Clinic. https://my.clevelandclinic.org/health/articles/circadian-rhythm

2. Ferreira, Â. (2019, July 26). Meal timing and weight loss: Is there a relationship? Blog Oficial Zumub.Com. https://www.zumub.com/blog/en/meal-timing-weight-loss-relationship/

3. Kant, A. K., & Graubard, B. I. (2015). 40-year trends in meal and snack eating behaviors of American adults. Journal of the Academy of Nutrition and Dietetics, 115(1), 50–63. https://doi.org/10.1016/j.jand.2014.06.354

4. Lee, D. Y., Jung, I., Park, S. Y., Yu, J. H., Kim, K. J., Kim, N. H., Yoo, H. J., Kim, S. G., Choi, K. M., Baik, S. H., & Kim, N. H. (n.d.). Attention to Innate Circadian Rhythm and the Impact of Its Disruption on Diabetes. Retrieved July 20, 2025, from https://www.e-dmj.org/journal/view.php?doi=10.4093%2Fdmj.2023.0193

5. Ofori-Asenso, R., Owen, A. J., & Liew, D. (2019). Skipping Breakfast and the Risk of Cardiovascular Disease and Death: A Systematic Review of Prospective Cohort Studies in Primary Prevention Settings. Journal of Cardiovascular Development and Disease, 6(3), 30. https://doi.org/10.3390/jcdd6030030

6. Smith, Y. (2016, March 6). What is the Circadian Rhythm? News-Medical. https://www.news-medical.net/health/Circadian-Rhythm.aspx

7. Snyder, C. (2023, June 21). Intermittent Fasting Methods Reviewed: Pros and Cons. Healthline. https://www.healthline.com/nutrition/6-ways-to-do-intermittent-fasting