It seems fibre really does go a long way. One of its breakdown products can ride through the blood stream of mice before settling in the brain, where it helps control hunger.
Much research into appetite has focused on the role that hormones play, but in the last few years researchers have found that mice can lose their appetite even if gut hormone levels remain unchanged. The latest work, by Gary Frost at Imperial College London and his colleagues, might help explain why.
The team found that mice on a high-fat diet gained weight less rapidly if fibre was added to their food. Next, they used scanners to track what happens to acetate – the most abundant fatty acid produced in the gut – when that fibre is broken down.
Traditional consensus is that such fatty acids make it as far as the liver, where they are metabolised. But to the researchers' surprise, they found that some of the acetate travelled all the way to the brain, where it settled in the hypothalamus – a region that helps control hunger. Injecting acetate into the brain also curbed the rodents' appetites.
If acetate does the same in humans, dietary fibre may hold the key to curbing appetites and perhaps help battle obesity – although boosting our intake might not be the best way to see an effect.
"The amount of fibre you need to eat to see consistent appetite suppression in humans is large – it's not just the amount you might eat in a bowl of bran flakes," says Frost. It might be more efficient to develop an acetate-based appetite-suppressing drug, or find a way to manipulate fibre so that more acetate is released in the gut, he says.
Journal reference: Nature Communications, DOI: 10.1038/ncomms4611
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