Stomach 'Clock' Tells Us When It's Time and How Much to Eat

Do you feel hungry? What about now? Scientists have discovered that timing is all important when it comes to eating. It turns out that nerves in the stomach act as a circadian clock, limiting food intake to specific times of the day. The findings shed light on how the gut signals to our brains about when we're full, and when to keep eating.

In order to learn a bit more about how our stomach reacts to hunger and when it signals that we're full, the researchers investigated how the nerves in the stomach respond to stretch at three-hourly intervals across one day. Stretch occurs as a consequence of food intake.

"These nerves are responsible for letting the brain know how much food we have eaten and when to stop eating," said Stephen Kentish, one of the researchers, in a news release. "What we've found is that the nerves in the gut are at their least sensitive at time periods associated with being awake. This means more food can be consumed before we feel full at times of high activity, when more energy is required."

While the stomach nerves are less sensitive during the day, though, they become far more sensitive during a change in the day-night cycle to a period associated with sleeping. Since they become more sensitive to stretch, they signal fullness to the brain more quickly and limit food intake. This variation repeats every 24 hours in a circadian manner, with the nerves acting as a clock to coordinate food intake. That said, these findings have only been made in laboratory studies and not in humans.

"Our theory is that the same variations in nerve responses exist in human stomachs, with the gut nerves being less sensitive to fullness during the day and more sensitive at night," said Kentish in a news release.

The findings could help researchers better understand how best to treat eating disorders. In addition, the new research could pave the way for future studies.

"We know that shift workers, for example, are more prone to disruptions in sleep and eating behavior, leading to obesity and other health problems," said Amanda Page, one of the researchers, in a news release. "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."

The findings are published in The Journal of Neuroscience.