Time to eat: What chrononutrition says about our health
By Rachel Firak, CCT
When’s dinner?! The answer to this question might be just as important as what’s on the menu.
We live in a fast-paced society that for many of us, pushes the limits on how much we can squeeze out of a day. Many of us work long hours, eat on the run, and don’t sleep enough. The neon signs of our city streets and the blue lights of our phones keep us up at night, along with late-night snacks containing stimulants like caffeine and sugar.
In Chinese medicine, we recognize the importance of balance between yin and yang. What does an abundance of daytime energy do to the part of us that needs rest and rejuvenation?
Almost every cell in the human body has been found to contain some version of a circadian clock. Studies back this up: deviations from natural circadian cycles have been shown to trigger inflammatory states, decreases in immune function and predispose one to cardiometabolic syndromes (heart attack, stroke, diabetes, and insulin resistance), even cancer (4). This suggests that synchronizing our patterns to the movements of the sun is actually a fundamental aspect of health.
The science of chrononutrition - how time, food, and health intersect - tells us this synchronization includes when we have meals. You’ve probably heard the cliche that breakfast is the most important meal of the day. Having breakfast decreases cortisol (the “stress hormone”) and helps prevent the development of insulin resistance. Shifting meals earlier as a practice, making sure our highest caloric intake is earlier in the day, can help us sleep better at night, stabilize hormone levels, and prevent obesity. As a contrast, having most of our caloric intake in the evening can trigger the development of metabolic syndrome, a state that predisposes a person to heart disease, stroke, and Type 2 diabetes (1).
Ending our last meal earlier is also associated with health benefits. The practice of minimizing the window in which meals are consumed is called Time-Restricted Eating, or TRE. TRE is associated with decreased insulin resistance and blood sugar level, greater glycemic control and glucose tolerance, and significant decreases in systolic blood pressure – comparable to that achieved by pharmaceuticals. Preliminary studies suggest it can also help prevent cancer recurrence. TRE windows that favor the earlier part of the day are more beneficial than TRE windows that favor the latter part of the day, with fewer benefits observed in those who stay up late, eat their last meal late, skip breakfast and have their first meal of the day in the afternoons (2).
Our bodies also seem better equipped to handle different kinds of foods at different times. For example, glucose tolerance peaks around midday and decreases with insulin secretion in the evenings, so carbohydrate consumption should ideally also follow that pattern, tapering off as the day goes on. Proteins cause satiating hormones to be released, but also promote melatonin which promotes sleep; they’re important to include in every meal, including dinner. In general, the body seems to work best when dinner is the lightest meal of the day, and is protein-based (1).
To summarize, it appears that our bodies are acutely aware of what time it is, and when we should (or shouldn’t) be eating. But even within a meal, it seems there’s an optimum timing to what one eats when - and how fast.
Eating meals faster, as one might expect, is associated with higher blood glucose spikes, insulin resistance, obesity, and higher risk of metabolic syndrome and type 2 diabetes than slow eating. However, for those who have to eat fast, eating vegetables first in a meal seems to eliminate much of these differences - which is important, because as researchers have pointed out, slow eating is not always easy to achieve (3). In other words, the best choice for health in any meal is eating slowly, with vegetables first. But the next best choice would actually be fast eating with vegetables first - better than slow eating with protein or carbohydrates first!
Timing is everything. Our bodies work best when we get up with the sun, eat breakfast and have an early (and light) dinner; when we eat our biggest and most carbohydrate-rich meals in the first half of the day; and from when we slowly, with vegetables first.
This research definitely lends new meaning to the phrase “time to eat”!
How does this information compare with your experience? Let us know in the comment section below :)
(1) Barrea, L., Frias-Toral, E., Aprano, S., Castellucci, B., Pugliese, G., Rodriguez-Veintimilla, D., Vitale, G., Gentilini, D., Colao, A., Savastano, S., & Muscogiuri, G. (2022). The clock diet: a practical nutritional guide to manage obesity through chrononutrition. Minerva Medica, 113(1), 172–188. https://doi.org/10.23736/S0026-4806.21.07207-4
(2) Adafer, R., Messaadi, W., Meddahi, M., Patey, A., Haderbache, A., Bayen, S., & Messaadi, N. (2020). Food Timing, Circadian Rhythm and Chrononutrition: A Systematic Review of Time-Restricted Eating's Effects on Human Health. Nutrients, 12(12), 3770. https://doi.org/10.3390/nu12123770
(3) Imai, S., Kajiyama, S., Kitta, K., Miyawaki, T., Matsumoto, S., Ozasa, N., Kajiyama, S., Hashimoto, Y., & Fukui, M. (2023). Eating Vegetables First Regardless of Eating Speed Has a Significant Reducing Effect on Postprandial Blood Glucose and Insulin in Young Healthy Women: Randomized Controlled Cross-Over Study. Nutrients, 15(5), 1174. https://doi.org/10.3390/nu15051174
(4) Lotti, S., Dinu, M., Colombini, B., Amedei, A., & Sofi, F. (2023). Circadian rhythms, gut microbiota, and diet: Possible implications for health. Nutrition, metabolism, and cardiovascular diseases : NMCD, 33(8), 1490–1500. https://doi.org/10.1016/j.numecd.2023.05.009