A study of protein-munching rats has shown a low-carbohydrate diet sparks a chain of biological events that ultimately curbs hunger.

According to French researchers, protein -- the staple of many weight-loss regimens -- appears to increase glucose production in the small intestine. Its rise is monitored by the liver, then registered by the brain. In turn, the brain sends out an "all full" message, cutting back on the drive to eat more.

"The latest findings provide an answer to the question, unsolved up to now, of how protein-enriched meals decrease hunger and reduce eating," the study's authors said.

"This novel understanding of the effect of diet protein will open new gates in the future medical treatments of obesity."

The researchers fed one group of rats a 50% protein diet enriched with soya protein and casein. Another group ate a starch-enriched diet that contained just 17% protein.

Reporting in the November issue of Cell Metabolism, the French team found, by the end of just one week, rats on the protein-rich regimen had consumed 15% less food.

The protein-diet rats also gained significantly less weight over the course of the week than the starch-diet rats, the study found. This was despite researchers including foods the rodents loved.

Even after food absorption had been completed, the small intestines of the protein-diet rats continued to deliver high levels of glucose into the portal vein -- a vessel that shuttles blood from the digestive system and other organs to the liver.

Glucose sensors in the liver of these protein-diet rats were found to have signaled those areas of the brain responsible for appetite control.

A quick and steady drop-off in both hunger and eating ensued.

The French team believes they have discovered a link between the digestive and central nervous systems.

Source: Sunday Telgraph (Sydney, Australia)