A study suggests that eating late at night increases the risk of cardiovascular disease.

Overview

Circadian cycles are the name for the physiological cycles that occur in human bodies and last roughly 24 hours.

These include cycles of eating and fasting that cause different tissues to establish peripheral clocks, which in turn help control how the heart and blood vessels function. A recent study aims to shed more light on this subject by investigating the relationship between changes in eating and fasting schedules and the prevalence of CVD.

Globally, CVD is the primary cause of illness and mortality. Dietary habits have a major impact on cardiovascular risk; poor diet has been connected to nearly 8 million deaths from CVD. Meal timings are frequently erratic since diets and traditional meal times have lost popularity in many segments of society in recent years.

However, the crucial new field of chrononutrition, which aims to clarify the web of relationships between meal timings and health, includes the relationship between cardiovascular health and the eating/fasting cycle.

Studies have indicated that eating breakfast is crucial for preserving a healthy metabolism and cardiovascular system, whereas eating late at night encourages obesity, arteriosclerosis, and abnormal lipid profiles. It also causes metabolic syndrome in females. Regarding the definition of late-night eating and the timing of each meal, there is a great deal of disagreement.

Eating within time constraints (TRE) may be a way to enhance cardiometabolic health. It is defined as prolonging the period of fasting at night to more than 12 hours. It has been associated with corresponding decreases in blood pressure, inflammation, and body weight in humans.

The current study was motivated by the relative lack of data on the direct effects of meal timing and duration of night fasting on CVD risk. The NutriNet-Sante study, which included over 100,000 adults, provided the data for the study, which was published in Nature Communications. They created a database on meal timing and frequency by using their dietary records.

What findings did the study make?

Individuals who were younger, single, had no family history of cardiovascular disease, regularly smoked, had higher levels of education, were more active, made less money each month, and were more likely to eat late breakfasts and late dinners.

People who ate their meals later were also more likely to have irregular meal schedules, binge drink, consume more alcohol on average, and go to bed later.

Seven years was the median follow-up period. Almost 700,000 person-years were covered by this. Just over 2,000 new cases of CVD were reported during this time, with the majority falling into the categories of coronary heart disease (CHD), which includes angina, angioplasty, acute coronary syndrome, and heart attacks, and cerebrovascular diseases, which include strokes and transient ischemic attacks.

The risk of CVD increased with the timing of the first meal; however, no such trend was seen with the timing of the last meal. On the other hand, the risk increased by 13% if it was consumed after 9 p.m. as opposed to before 8 p.m. Every hour that passed after the last meal increased the risk of cerebrovascular disease by 8%, reaching a 28% increase at the inflection point (after 9 p.m. versus before 8 p.m.).  

An increase in nighttime fasting was associated with a 7% lower risk of cerebrovascular disease; however, no comparable decline was seen for CHD or for CVD as a whole.

The risk of cardiovascular outcomes was thus elevated, more so in women than in men, if the first meal was eaten after 9 am as opposed to before 8 am, and if the last meal was taken after 9 pm as opposed to before 8 pm. Women also benefited from longer nightly fasting intervals more than men did.

The greatest advantages seem to occur when nighttime fasting intervals are extended by moving up the time of the evening meal instead of postponing or missing the morning meal. This is most likely due to the fact that people become less sensitive to insulin and higher glucose levels throughout the day after they wake up.

In fact, when breakfast was routinely postponed by four hours, animal studies show the onset of weight gain, increased fat mass, fat deposition in the liver, and a delay in the rhythmic expression of lipid metabolism genes.

Studies on humans show that delaying evening meals is associated with abnormalities in insulin sensitivity and glucose regulation, dyslipidemia, and weight gain that exceeds normal limits.

Food consumption during the body's rest phase, when melatonin secretion is at its highest, may be connected to this, as it results in prolonged blood glucose elevations following meals.

What ramifications result?

An earlier finding from the same cohort suggests that early TRE, with early first and last meals, is best for cardiometabolic health. Individuals who fasted for more than 13 hours overnight and had breakfast before 8 am were found to have a lower risk of type 2 diabetes mellitus.

The results, which show that eating later for both the first and last meal is associated with a higher risk of CVD overall, support previous research that found that eating earlier for breakfast and dinner improved cardiometabolic risk factors. Eating at the appropriate times has been shown to speed up the metabolism of food because it triggers peripheral circadian rhythms that control blood pressure.

Although these results are encouraging, confounding variables such as the potential for night shift work among those who eat later in the evening must be taken into account due to the large sample size and prospective design.

This is a separate predictor of both poor sleep and cerebrovascular illness. To rule out shift work of this kind, none of the study participants ate meals unusually early or late.

Additional factors that were not controlled for in this study but may potentially cause circadian rhythm disturbances include drinking, substance abuse, exercise or other activity timing, nighttime awakenings, and light exposure.