© Nadin Sh
September 15, 2026
Marianne Waldenfels
During the week we eat breakfast early; on days off, hours later — and dinner shifts too. A new study of more than 100,000 adults suggests that "eating jetlag" may be harder on the heart than previously thought.
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Healthy eating has long been a science in its own right. We count proteins, pay attention to fiber, debate which fats are harmful and how late dinner should really be. Yet there is one surprisingly simple question we rarely ask: do we actually eat at roughly the same time every day?
A new study of more than 100,000 adults suggests that this could indeed matter for health. In men, larger shifts in meal times between working days and days off were associated with a higher risk of cardiovascular disease. What seemed to matter was not whether meals shifted earlier or later, but how much the usual rhythm changed.
Researchers call this "eating jetlag" — a phenomenon many people will recognize from their own lives, even if they have never put a name to it.
Someone who gets up at six on weekdays but sleeps until ten on weekends effectively lives by a different rhythm on their days off. In research, this is known as "social jetlag." Eating jetlag works the same way — only with meals.
For this study, researchers compared meal times on working days and days off, using the midpoint of the daily eating window as the key measure. Someone who eats between 7 a.m. and 7 p.m. during the week, for example, has an eating midpoint of 1 p.m. If that window shifts to 10 a.m. to 10 p.m. on weekends, the midpoint moves three hours later.
Most participants kept their meal times relatively consistent. Even so, nearly one in four shifted their eating rhythm by more than an hour later on days off, while a smaller group shifted it more than an hour earlier.
The participants in the French NutriNet-Santé cohort recorded in detail what they ate and when, and were followed for just over eight years.
In men, each additional hour of eating jetlag was associated with a 14 percent higher risk of cardiovascular disease . For coronary heart disease specifically, the figure was 21 percent.
Notably, it was not only later meal times that stood out. Men who shifted their meals significantly earlier on days off also showed a higher risk — which argues against late dinners alone being responsible for the association.
The data do not, however, point to a fixed threshold at which shifting meal times becomes problematic. The risk increased with greater eating jetlag but leveled off once the shift exceeded roughly one and a half hours.
The body keeps no appointment calendar — and yet it has a fairly precise sense of when food normally arrives. Eating is one of the key signals by which our internal rhythms orient themselves.
While the central internal clock in the brain responds primarily to the alternation of light and darkness, food plays an important role for metabolic organs such as the liver and pancreas. Regular cycles of eating and fasting help to keep various metabolic processes in sync.
When meals repeatedly shift by several hours, these processes may become less well coordinated. Controlled experiments support this: metabolism does respond to changes in meal timing. In a small study of healthy young adults , even a one-hour delay in dinner affected blood sugar levels after the meal.
Whether such short-term effects can explain why more cardiovascular events occurred years later in the current study remains an open question. It is conceivable that several long-term processes are involved — including the regulation of blood sugar, insulin, fat metabolism, and blood pressure.
The distinction matters. Chrononutrition is concerned primarily with when we eat: is an early breakfast better than a late one? Should the largest meal of the day be at midday rather than in the evening?
Eating jetlag, by contrast, is about how much a person's own meal times vary from one day to the next.
Someone who eats dinner at around 9 p.m. every evening has a relatively stable rhythm — late, perhaps, but consistent. Someone who has dinner at 6 p.m. during the week and not until 10 p.m. on weekends is shifting it by several hours.
This study therefore does not answer the question of the ideal time for breakfast or dinner. Rather, it suggests that alongside the timing of meals, their consistency may also be important.
One question the study leaves particularly open is why the association between eating jetlag and cardiovascular disease was not found in women.
No confirmed explanation exists yet. Biological differences could play a role, as could differences in lifestyle. Whether men are genuinely more sensitive to eating jetlag remains to be investigated.
No. Breakfast does not need to happen at exactly seven o'clock every morning, and this study does not turn Sunday brunch into a health risk.
Further research is needed to determine how much influence shifting meal times actually has, and whether a more consistent eating rhythm can help protect the heart.
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