Science can’t seem to draw a bead on breakfast. Your grandmother has always said it’s the most important meal of the day, and some studies have found healthier outcomes among breakfast eaters. But more research argues breakfast adds unnecessary calories to your daily diet.

So which side is right? Dig deep into the existing literature, and the picture becomes clearer: We should all be eating breakfast—and not just a nibble of egg or toast.

A recent study from Harvard Medical School and Spanish researchers found people who ate their biggest meal of the day in the a.m. lost 25% more weight than those who ate their main meal later in the day. Another Harvard study found breakfast skippers has a 27% greater risk of suffering a heart attack or death from coronary heart disease.

Unlike some of the anti-breakfast research—nearly all of which is correlational, and so could be skewed by a number of factors—the pro-breakfast studies stand on firmer scientific foundations. The really compelling stuff has to do with your body’s natural circadian rhythms, or “clocks.”

This gets complicated in a hurry. But in simple terms, your sleep, appetite, energy levels, and much else depend on these internal clocks. When they’re off, you may struggle to sleep, feel wiped out during the day, and tend to get hungry at odd times—or all the time.

Up until a few years ago, most of the research on circadian rhythms focused on sleep. (Shift workers who have to operate on wonky schedules may suffer from higher rates of cancer and other diseases, studies show.) But new research indicates when and how you eat also plays an important role.

A study from the Yale School of Medicine found eating soon after waking tells your brain and body it’s time to start your day’s clock. The study authors say skipping a meal in the morning de-couples your “central” circadian clock—which takes its cues from light and body temperature—from your “peripheral” circadian clock, which is regulated by meal timing.

When you skip breakfast, the Yale research shows, your whole eating schedule is thrown forward. That causes your hunger to spike in the evening and after-dark hours, and may drive both over-eating and poor sleep.

Give it some thought, and eating a large breakfast and smaller dinner makes a lot of sense. Food is fuel. And you need fuel most during the day when your brain and body are working, not at night when you’re resting or sleeping. The modern habit of skipping breakfast and eating a massive dinner is unnatural—something we forced on our bodies because of societal custom, the research suggests.

If you’re not convinced, observe the eating habits of infants and toddlers. They tend to slam a big breakfast but are finicky about eating later in the day. Eventually, as they age, their parents retrain them to eat a big dinner. But it’s us grownups who should be taking cues from our kids, not the other way around, the research suggests.

So what’s the takeaway? Eating a big morning meal, ideally one packed with protein and fiber, and tapering your food intake as the day wears on is a smart move for your health. That may seem tough at first. But stick with it for two months—66 days, to be exact—and your new habit should take hold, according to a University College London study.