In a study led by Imperial College London and the Medical Research Council (MRC), an international team of researchers identified an anti-appetite molecule called acetate that is naturally released when we digest fibre in the gut.
    
Once released, the acetate is transported to the brain where it produces a signal to tell us to stop eating.
    
The study also found that acetate reduces appetite when directly applied into the bloodstream, the colon or the brain.
    
When fibre is digested by bacteria in our colon, it ferments and releases large amounts of acetate as a waste product.
    
The study tracked the pathway of acetate from the colon to the brain and identified some of the mechanisms that enable it to influence appetite.
    
"The average diet in Europe today contains about 15 g of fibre per day," said lead author of the study Professor Gary Frost, from the Department of Medicine at Imperial College London.
    
"In stone-age times we ate about 100g per day but now we favour low-fibre ready-made meals over vegetables, pulses and other sources of fibre.
    
"Unfortunately our digestive system has not yet evolved to deal with this modern diet and this mismatch contributes to the current obesity epidemic.
    
"Our research has shown that the release of acetate is central to how fibre suppresses our appetite and this could help scientists to tackle overeating," Frost said.
    
The study analysed the effects of a form of dietary fibre called inulin which comes from chicory and sugar beets and is also added to cereal bars.
    
Using a mouse model, researchers demonstrated that mice fed on a high fat diet with added inulin ate less and gained less weight than mice fed on a high fat diet with no insulin.
    
Further analysis showed that the mice fed on a diet containing inulin had a high level of acetate in their guts.
    
Using positron emission tomography (PET) scans, the researchers tracked the acetate through the body from the colon to the liver and the heart and showed that it eventually ended up in the hypothalamus region of the brain, which controls hunger.
    
In collaboration with Consejo Superior de Investigaciones Cientificas (CSIC) in Madrid, the researchers investigated the effects of acetate in the hypothalamus.
    
The researchers found that the acetate accumulates in the hypothalamus after fibre has been digested.
    
"The acetate then triggers a series of chemical events in the hypothalamus leading to the firing of pro-opiomelanocortin (POMPC) neurons, which are known to suppress appetite," said Professor Sebastian Cerdan from CSIC.
    
The research is published in the journal Nature Communications.

(Agencies)

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