STOMACH CLOCK REGULATES WHEN WE'RE HUNGRY

Researchers say they have uncovered the first evidence that nerves situated in the stomach follow a circadian rhythm and limit a person's food intake to certain times throughout the day. This is according to a study published in The Journal of Neuroscience.
Investigators from the University of Adelaide in Australia say their findings may lead to insight into how the stomach tells the brain we are hungry or full.

Lead study author Stephen Kentish, investigated how the nerves in the stomach respond to stretch, which occurs as a consequence of food intake at approximately three-hour intervals throughout the day.

"These nerves are responsible for letting the brain know how much food we have eaten and when to stop eating," Kentish said. "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.
However, with a change in the day-night cycle to a period associated with sleeping, the nerves in the stomach become more sensitive to stretch, signaling fullness to the brain quicker and thus limiting food intake. This variation repeats every 24 hours in a circadian manner, with the nerves acting as a clock to coordinate food intake with energy requirements," he said in a statement.

Following on from this work, the researchers also found that these nerve cells expressed a set of "circadian clock" genes that are also expressed in the brain region that regulates the wider circadian rhythm of the body. In other words, the researchers say, these nerve cells appear to form a kind of neural clock in the stomach, regulating the amount of food needed to elicit fullness during the day and night.

Kentish and his colleagues' work is based on laboratory studies, not on human tests.
"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," Kentish said.
Amanda Page, another researcher involved in the study said the research could lead to more information on how changes in people's circadian clocks affects their eating habits.
"We know that shift workers, for example, are more prone to disruptions in sleep and eating behavior, leading to obesity and other health problems."

Previous research has suggested that nurses who work long shifts, overtime or other adverse work schedules may be more prone to obesity. 

The investigators of University of Adelaide say they are now conducting further research to see how changes to the circadian rhythm impacts eating behavior, and how the nerves in the stomach react to the changes. The team says "We want to see how these systems can be disrupted by shift work and obesity".

Sources: http://www.adelaide.edu.au/, http://www.abc.net.au/science/, http://www.medicaldaily.com/, http://www.medicalnewstoday.com/