Who Invented Three Meals a Day?
At eleven at night, half the office lights are still on. Delivery riders queue downstairs, the convenience-store oden pot is steaming, and the night-market stalls are just setting up. For many young people today, this is the first proper meal of their day. Breakfast was slept through. Lunch was improvised.
The older generation shakes its head at the scene. Three meals a day is the rule handed down for generations — how can it be broken? The young answer is just as crisp: eat when you are hungry. Is that not closer to what the body wants?
The argument is really about two questions: how many meals, and at what times. Over the past two decades, researchers have carefully audited both. The result: each side is only a little bit right.
Start with the ancestry of the three-meal day. It is not written into our genes. In ancient Rome, respectable citizens ate one main meal a day. In agrarian Europe, most people ate twice, following the sun. What pinned eating into three fixed slots — morning, noon, night — was the factory bell of the Industrial Revolution: a meal before the shift, a meal at the midday break, a meal after work. Eating was scheduled by someone else's timetable for the first time in history. As for "breakfast is the most important meal of the day," food historians trace the phrase to cereal advertising in the early twentieth century. It was sold, not discovered.
Three meals a day is a product of the work schedule. That origin matters: it deserves respect, but it is not a law of physiology.
So what does the laboratory say about meal frequency? The method is simple: lock total calories in place, feed one group three meals and another six, and see who loses more weight and whose metabolism improves. A 2015 meta-analysis in Nutrition Reviews, pooling 15 randomized controlled trials, found that the apparent edge of frequent small meals vanished once a single outlying study was removed. With calories held equal, how often you eat has no reliable effect on weight loss or metabolic rate. A 2024 analysis in JAMA Network Open, pooling 29 trials and 2,485 people, found the lower-frequency group lost about 1.85 kilograms more — but the authors themselves called the effect small, of uncertain clinical importance, with most trials at high risk of bias. And in a widely cited 2014 trial in Diabetologia, 54 patients with type 2 diabetes eating the same calories did better on two meals, breakfast and lunch, than on six: more weight loss, less liver fat, better insulin sensitivity.
Taken together, the trials point to one sentence: total intake decides first. Meal frequency comes far behind — nowhere near as important as the two camps claim.
The real dividing line is the clock. The field has a name: chrononutrition. Marta Garaulet's team at the University of Murcia followed more than 3,300 people through a weight-loss program: late eaters lost about 17 percent less weight than early eaters. In a study of more than 19,000 women, those whose dinner fell within two hours of bedtime, or who snacked after dinner, were markedly more likely to have overweight or obesity. A controlled experiment at Johns Hopkins made it vivid: the identical meal eaten at 10 p.m. produced blood-sugar peaks about 20 percent higher and overnight fat burning about 10 percent lower than the same meal eaten at 6 p.m. A 2025 twin study went further: people who consumed half their calories in the later half of their own circadian day had insulin sensitivity roughly 30 percent lower — regardless of how much they ate. Timing, not quantity.
That is precisely where the young lifestyle takes its hit. Sleeping late is not the sin, and the skipped breakfast is not the point. The damage is that the whole eating window slides toward midnight, and with late dinners and night snacks, most of the day's calories land in the hours when the body handles them worst. Researchers call the mismatch between the body clock and the social clock "social jet lag." The unease about that 11 p.m. meal is not that it breaks a rule. It is that it pays the bill for an entire shifted rhythm.
Now the other side: eating when hungry. In the literature it has a formal name, intuitive eating — no clock, no meal plan, letting hunger and fullness signals decide when to start and stop. The supporting evidence is real. Project EAT at the University of Minnesota surveyed 2,287 young adults averaging 25 years of age: those who trusted their body's signals had lower body mass index and fewer disordered behaviors such as binge eating and chronic dieting. An eight-year longitudinal follow-up of the same project found the same direction. A 2021 meta-analysis of 97 studies likewise found that higher intuitive-eating scores came with fewer eating-disorder symptoms and better body image.
But this body of evidence has a shared weakness: most of it is observational. It shows that people who can read their body's signals are healthier. It cannot show which caused which. It may be the reverse — that people with orderly lives, never battered by dieting, are the ones whose hunger signals survived intact. And hunger is not always a reliable instrument. Short sleep, stress and a history of restriction can all break it: silent when it should ring, ringing when it should not.
Nowhere is that clearer than in an eating-disorder ward. The international standard treatment, enhanced cognitive behavior therapy (CBT-E), developed at Oxford, begins by reversing "eat when hungry" entirely: eat by the clock. Three planned meals plus two or three planned snacks, never more than about four hours apart, whether you feel hungry or not. Britain's National Institute for Health and Care Excellence recommends the same. The logic is plain: for these patients, the hunger signal is part of the illness. Waiting for it before eating means not eating. An external rhythm has to feed the body steadily before the internal signal can slowly repair itself.
So one question yields two answers. For metabolically healthy adults, frequency and punctuality are flexible, as long as total intake and timing are roughly right. For people whose signals have already failed, regularity is not a constraint — it is the treatment. That is why the argument never produces a winner: the two sides are not talking about the same people.
Back to the table at eleven at night. Science has not issued modern life a new rulebook. It has simply ranked what matters: total intake first, timing second, regularity third, meal count last. Three meals a day is not a commandment; it is a legacy of the factory age. Eating when hungry is not a master key either; it works for intact signals and endangers broken ones.
The way a person eats is always arranged by life first: once by the factory bell, then by the office light, now by the phone screen and the midnight delivery app. The better question may not be how many meals a day we owe ourselves, but whether, inside a schedule packed by everything else, we can still leave the body a stretch of time that belongs to it.
(Editor's note: This feature summarizes published research on a health topic and does not constitute individual medical advice. People with eating disorders, diabetes or other metabolic conditions should follow their clinician's advice.)
Published by GSM · USA (original Chinese edition)
Photo: 图：一桌家常饭菜，桌上一碗洗净的红提。图片来源：James 提供。 / Photo: A home-cooked family dinner with a bowl of red grapes. Image provided by James.
