According to a new populational study, timing meals to natural circadian rhythms and maintaining a long nightly fast is positively associated with cardiovascular health, especially in women [1].
The natural rhythms
Diet is one of the most powerful modulators of health and longevity. The amount, type, and timing of meals are all important. Like most animals, humans have circadian rhythms that adapt us to the cycle of day and night. Circadian programs are hard-wired into our genes, regulating everything, including food metabolism [2].
However, this can be affected by the modern way of life, which allows people to deviate considerably from those natural rhythms. In a new study published in Nature Communications, the researchers analyzed data from a large cohort of more than 100,000 people to reveal associations between the timing of meals and the incidence of cardiovascular diseases (CVD).
Over seven years of follow-up on average, about 2,000 cardiovascular events were recorded. This is surprisingly few considering the cohort size, but it is explainable by the relatively young mean age of 42.6 years. The cohort was also skewed towards women (79%). Later first and last meals were disproportionately reported by younger participants, students, or unemployed people. The “late eaters” were also more often single, drinkers, and smokers, and they had higher average levels of physical activity. In short, when we’re young and active, we party, go to bed late, and sleep in; there were no surprises here.
Early meals win
The researchers found that even after controlling for all these and some other variables, each additional hour in delaying the time of the first meal of the day was associated with a 6% increase in overall CVD risk. However, the timing of the last meal of the day did not show a significant association. Specifically with cerebrovascular diseases, the relationship was reversed: the time of the first meal was insignificant, but later last meals were associated with an increase in risk.
When “before 8 pm” was taken as a reference, “between 8 and 9 pm” was associated with a 19% increase in risk, and “after 9 pm” had a 28% increase. No association was observed for many other meal timings. When cerebrovascular diseases were decoupled from coronary heart diseases, no significant effects on risk were found in the latter category.
When stratified by sex, associations were generally stronger for women. Later times of first and last meals were significantly associated with a higher risk of overall CVD and cerebrovascular disease for women but not for men. The picture was reversed for coronary heart diseases, where associations were significant in men but not in women.
Start fasting earlier, do it for longer
The researchers found that nighttime fasting duration was inversely associated with cerebrovascular disease risk. Each additional hour of fasting lowered the risk by 7%. However, no such association was found for coronary heart disease or overall CVD. The time interval between the last meal and bedtime was inversely associated with the risk of overall CVD, with the best possible interval being four hours.
The researchers suggest that their findings “are in line with the growing body of evidence on time-restricted eating and its positive impact on markers of cardiometabolic health in humans such as reduced blood pressure, increased insulin sensitivity, and reduced body weight.”
However, the study also suggests that there is a role for the timing of the daily fast. “It is reasonable to think”, the paper continues, “that it would be better to practice time-restricted eating by having an early first and last meal of the day.” A study from last year found that early time-restricted feeding (eTRF) was more effective than mid-day TRF at improving insulin sensitivity. Moreover, only eTRF improved fasting glucose, reduced body mass, adiposity, and inflammation while increasing microbiome diversity [3].
Like any populational study, this one should be taken with a grain of salt. For lifestyle factors such as diet, it is all but impossible to effectively control for all the confounding variables. The study’s limitations include its relatively young cohort and subsequently few adverse events along with the nearly 4:1 female-to-male ratio. However, for now, it looks like eating early first and last meals of the day and maintaining a nightly fast of 13 hours or more might be a sensible strategy.
Literature
[1] Palomar-Cros, A., Andreeva, V. A., Fezeu, L. K., Julia, C., Bellicha, A., Kesse-Guyot, E., … & Srour, B. (2023). Dietary circadian rhythms and cardiovascular disease risk in the prospective NutriNet-Santé cohort. Nature Communications, 14(1), 1-12.
[2] Chamorro, R., Jouffe, C., Oster, H., Uhlenhaut, N. H., & Meyhöfer, S. M. (2023). When should I eat: A circadian view on food intake and metabolic regulation. Acta Physiologica, 237(3), e13936.
[3] Xie, Z., Sun, Y., Ye, Y., Hu, D., Zhang, H., He, Z., … & Mao, Y. (2022). Randomized controlled trial for time-restricted eating in healthy volunteers without obesity. Nature communications, 13(1), 1003.
