New Australian research has uncovered the presence of a 'circadian clock' in our stomachs which limits food intake to specific times of the day. It is thought that these gut signals could help people limit the amount of food they eat and reduce the risk of obesity simply by syncing their meals with their tummy clocks. The main key is to sleep regular hours and avoid eating late at night.
Belly clock picture from Shutterstock
Researchers from the University of Adelaide studied clock gene expression in mice to determine whether circadian variation may play a role in regulating the amount of food that can be consumed before satiation is reached. During the experiment, scientists analysed how nerves in mice stomachs responded to stretch, which occurs as a consequence of food intake, at three-hourly intervals across one day.
They discovered that the mice's appetites exhibited different sensitivity depending on the time of day:
The identification of clock genes in the nodose ganglia is the first evidence to suggest that vagal afferents may act as a peripheral clock. Meal size in rodents varies dramatically between the light phase and dark phase with both increased frequency and size being reported in rats during the dark phase
While the experiment was limited to mice, it is thought that the same signals sent from the gut to the brain are also present in humans. This information could therefore lead to nutritional breakthroughs in the areas of obesity and overeating.
"We've found is that the nerves in the gut are at their least sensitive at time periods associated with being awake," said chief researcher Dr Stephen Kentish. "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, signalling 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."
This also helps to explain why shift workers are more prone to disruptions in eating behaviour, which often leads to obesity and other health problems — simply put, their circadian clocks are all out of whack.
The research team are now conducting further research to see what kind of impact such changes to the circadian rhythm will have on eating behaviour, and how the nerves in the stomach react to those changes.
Circadian Variation in Gastric Vagal Afferent Mechanosensitivity [The Journal of Neuroscience]