Could overeating be all about the gut-brain feedback loop?
Is it time to go back to the drawing board when it comes to our understanding of why some folks can’t stop eating too much?
Your Back Page scribbler has never questioned that the factors governing the urge to overindulge in food might be complex, but we’ve always assumed hunger, flavour, aroma, psychology, genetics and social and environmental circumstances might all play some sort of contributing role.
But, according to research published this month in the journal Current Biology, what we’ve been failing to consider in this complicated equation is the joy of swallowing.
Writing in a paper bogglingly titled “Serotonergic modulation of swallowing in a complete fly vagus nerve connectome”, an international consortium of scientists set out to show that humans possess a “gut-brain feedback loop”, which is essentially a mechanism that keeps folks coming back for more.
Their theory suggests that once a piece of food passes through the oesophagus, the brain releases a shot of the hormone serotonin as a positive encouragement to do that swallowing thing again.
Or as our boffins put it: “We identify a gut-brain feedback loop in which Piezo-expressing mechanosensory neurons in the oesophagus convey food passage information to a cluster of six serotonergic neurons in the brain. Together with information on food value, these central serotonergic neurons enhance the activity of serotonin receptor 7-expressing motor neurons that drive swallowing.”
The research team came to this conclusion by thinly slicing up the larvae of fruit flies then using an electron microscope to examine how the baby bugs’ nerve cells worked together during the digestion process.
What they found was the oesophagus contains what they call a “stretch receptor” which is responsible for sending a nerve signal to the brain telling it that the oesophagus is processing food.
And that is important, our scientists argue, because: “If [that ‘stretch receptor’] is defective, it could potentially cause eating disorders such as anorexia or binge eating. It may therefore be possible that the results of this basic research could also have implications for the treatment of such disorders.”
What this doesn’t explain, however, is why eating some foods is more pleasurable than others.
We would suggest that if it’s only the swallowing that is the fun bit, then folks wanting to lose weight would be just as happy chowing down lettuce leaves and cucumber slices as they would be French fries and Tim Tams.
So there may just be a bit more to find out on the human brain chemistry front before we start shorting our Novo Nordisk shares.
Send easily digestible story bites to penny@medicalrepublic.com.au.
