Stomach Gets Hunger Cues from Circadian Rhythm, New Study Finds

For anyone wondering how on earth the Spanish can wait until 10 p.m. for dinner, science now has an answer. New laboratory research from the University of Adelaide, published in the Journal of Neuroscience, indicates that nerve cells in the stomach act as a circadian clock, effectively controlling when the body gets its hunger cues. The new research also helps us understand how the stomach knows when it's full.

This circadian rhythm has everything to do with how we eat. "[Nerve sensitivity] variation repeats every 24 hours in a circadian manner, with the nerves acting as a clock to coordinate food intake with energy requirements," lead author Dr. Stephen Kentish said.

So the sensitivity of the nerves help determine how much food we eat: when the body knows it's going to be active, the nerves aren't as sensitive to stomach stretch (meaning you eat more), and they don't tell the brain you're full as quickly — calories, after all, are units of energy.

If you're used to sleeping at night, you won't require as much energy, so your nerve cells will be more sensitive in an effort to control your food intake. But if you were used to snacking late at night, your meals are likely going to be pretty dinner-heavy in the years after. Basically, you're going to feel like eating later as a result of your body anticipating the need for later energy.

The study, done only in a laboratory context so far, has huge implications for the world of nutritional science: circadian rhythms are hard to shake — which could explain why long-term eating patterns are hard to shake (switching to snacking after being a three-square-meals sort of person, for example, or getting used to having a big breakfast instead of a big dinner).

"We are now conducting further research to see what kind of impact such changes to the circadian rhythm will have on eating behavior and how the nerves in the stomach react to those changes," study leader Amanda Page said.