Closing the computer late, shuffling home and sitting down to dinner at ten at night. For us it is a picture of customs; For the rest of Europe, an incomprehensible eccentricity. However, the shock is not only cultural but also biological. Although our social “normality” dictates that dinner is served after dark, our body tells a very different story. Evolutionarily, our body is not designed to digest large amounts of food when the sun has set.
It’s not just about counting the calories we put on the plate; The real problem, the one that acts as a real time bomb for our health, is what the clock ticks when we put the fork in our mouth. Eating dinner late is altering our metabolism, sabotaging our quality of sleep and, silently, increasing our cardiovascular risk.
Your pancreas doesn’t know that in Spain they have late dinners. To understand this phenomenon, we must look to the chrononutritionan emerging field of study investigating the close relationship between food intake and circadian rhythms. Our body works like an orchestra perfectly synchronized by light and darkness.
By eating dinner at odd hours we are desynchronizing “peripheral watches” of vital cells located in the pancreas or liver. Meal timing acts as a critical signal for these peripheral biological clocks, which can modulate the quality of our sleep by regulating the rhythm of our central clock. The immediate consequence is a drastic worsening of glucose tolerance and insulin secretion.
When we really should be sleeping. Here the body comes into conflict. On the one hand, there is a large release of cortisol (the well-known stress hormone) and, on the other, the release of melatonin is delayed, which is the master key to falling asleep. In fact, large-scale data support this: comprehensive analyzes of chrononutrition patterns reveal that later meal times—including the first meal, middle meal, and last meal of the day—as well as greater number of meals, are directly associated with higher scores on the Pittsburgh Sleep Quality Index (PSQI), which translates into a worse rest.
Added to this is a problem purely mechanical: A reduced time gap between the last meal and bedtime can lead to a prolonged sleep latency period, that is, we toss and turn more before falling asleep. And digesting while lying down is the perfect recipe for the appearance of gastric reflux, a discomfort that can ruin anyone’s night.
You eat the same as your early-rising neighbor and you gain more weight. According to the study published in The Journal of Clinical Endocrinology and Metabolismadults who eat dinner at 10:00 p.m. burn 10% less fat and suffer a 20% higher blood sugar spike than those who eat dinner at 6:00 p.m., even if both groups eat exactly the same and go to bed at the same time. Alexis Supan, dietician at the Cleveland Clinic, summed it up perfectly: “When you eat late at night you are going against your body’s circadian rhythm.” The natural limit should be marked by the beginning of melatonin secretion.
The researcher Marta Garaulet, a world reference in chrononutrition, has already demonstrated that people who eat later at midday lose less weight than those who eat early, even when they consume the same calories, expend the same energy and sleep the same. The time alone makes the difference.
The consequences of ignoring this limit go far beyond the scale. A study led by the institute ISGlobalbased on cohort NutriNet-Santé with more than 100,000 participants, concluded that dining after 9:00 p.m. It is associated with increased cardiovascular risk, especially impacting the risk of cerebrovascular disease in women. On an emotional level, a recent meta-analysis from 2025 details that eating late worsens the rhythms of key neurotransmitters such as serotonin and dopamine, increasing the risk of depression.
On top of that we hit the same clock twice. But there is a modern factor that makes this scenario worse: screens. Not only do we eat dinner late, but we do so under the beam of our cell phones. Light of any kind suppresses melatonin, but as you warn harvardthe blue night light does it in a much more powerful way, blocking it for twice as long as other lights and moving our circadian rhythms out of phase by up to three hours. Recent clinical studies have demonstrated that exposure to blue LED light significantly suppresses melatonin secretion after two hours of exposure and maintains this suppression over time. We have a late dinner and then look at our phones in bed: a combination that our biological clock simply cannot accommodate.
Our children are headed towards the same error. The problem worsens when we look at the new generations. The magazine The Lancet has warned that Spain could be the fourth country in the world with the highest childhood obesity in 2050. The VALORNUT project of the Complutense University has shed light on this: Late dinners and very long “eating windows” in children translate into more improvised diets, with lower nutritional value and worse cholesterol profiles. Furthermore, 60% of these children sleep fewer hours. The experts’ recommendation it’s clear: concentrate all meals in a period of less than 12 hours.
The solution is to adjust the clock. So when should we have dinner? The golden rule agreed upon by experts is to allow between three and four hours to pass between the last meal and the time of going to sleep. If we take the Spanish average of going to bed around 00:30, we should be finishing dinner, at the latest, at 21:00.
Here it is important to qualify the context. We have been cushioning this metabolic blow in part for decades thanks to a cultural pillar: the Spanish Mediterranean diet tends to make dinner a much lighter meal than the midday meal, leaving the energy weight of the day in earlier hours. A late, heavy, ultra-processed dinner followed by a trip straight to bed is not the same as a light dinner with some physical activity before going to sleep. That nuance matters.
What does not allow nuances is the direction that science points. If your appetite hits at the last minute, a light snack based on fruits or vegetables is perfectly valid, always away from alcohol and caffeine. But if we want to curb obesity, take care of our hearts, and get back to sleeping soundly, we must accept a new nutritional reality: when we eat has become exactly as important as what we eat. It’s time to resynchronize our dishes with the sun.
Image | Magnificent
Xataka | In Spain we love to have dinner at ten at night. To our biological clock and our heart, not so much
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