A tablet that turns off hunger is on the horizon after scientists found how high-fibre foods tell the body to stop eating.
The reason that people feel full when eating fruit and vegetables is because fibre, of which they are a good source, releases acetate into the gut, scientists found. The molecule then travels to the brain and suppresses appetite.
The scientists believe a pill derived from acetate could help people cut how much they eat without experiencing cravings.
One in four adults in England is obese and that figure is expected to climb to six in 10 men and one in two women by 2050. Obesity and diabetes costs the NHS more than 5 billion pounds every year and that is likely to rise to 50 billion.
Acetate is released in the gut when plants and vegetables are digested.
The scientists tracked the molecule and found that it ended up in the hypothalamus region of the brain, which controls hunger.
Their study suggests that obesity may have become an epidemic because the healthy diet of the past has been replaced with processed food, which does not produce acetate when digested. As a result, the brain does not receive a signal telling it to stop eating.
The average modern diet in Europe contains about 15g of fibre per day. In Stone Age times it was around 100g.
"Unfortunately our digestive system has not yet evolved to deal with this modern diet,'' said Prof Gary Frost, of Imperial College London.
Although the scientists say their research should encourage people to eat more fruit and vegetables, they also believe it could pave the way for new drugs to help dieters.
"The major challenge is to develop an approach that will deliver the amount of acetate needed to suppress appetite but in a form that is acceptable and safe for humans," Prof Frost said.
The study analysed the effects of a dietary fibre called inulin which is found in chicory and sugar beet and is added to cereal bars.
Experiments on mice found those fed on a high-fat diet with added inulin ate less and gained less weight than animals given the same diet with no inulin. Researchers noticed that the acetate released in digestion accumulated in the brain where it caused neurons to fire, suppressing hunger.
The study also showed that when acetate was injected into the bloodstream, colon or brain it reduced the amount of food eaten by the mice.
Prof Jimmy Bell, of the Medical Research Council's clinical sciences centre at Imperial, who collaborated in the research, said: "We have started to really understand what lies behind fibre's natural ability to suppress our appetite and identified acetate as essential to the process.
"In the context of the growing rates of obesity in western countries, the findings of the research could inform potential methods to prevent weight gain."
Acetate is only active for a short time in the body so any pill would need to mimic the chemical's slow release during digestion in the gut.
Prof David Lomas, chairman of the MRC's population and systems medicine board, said it was becoming increasingly clear that the interaction between the gut and the brain played a key role in controlling how much people eat.
"Being able to influence this relationship, for example using acetate to suppress appetite, may in future lead to new, non-surgical treatments for obesity."
- The Daily Telegraph