Struggling with that post-holiday diet? The good news is that scientists in China have discovered that humans may have a natural mechanism to shut off appetite.

The catch is that the research, for now, appears to apply primarily to one part of a healthy diet: protein. Still, it provides a ray of hope to dieters everywhere.

Li Yan at the Chinese Academy of Sciences' Institute of Biophysics recently published the results of a study into the dietary habits of fruit flies. The study suggests that organisms have a nutrient-sensing regulator that controls protein levels in the body.

Her research team observed that after eating a large high-protein meal, fruit flies will stop consuming protein thanks to a peptide known as FIT, which reduces appetite, according to the findings in Nature Communications, an international science journal.

"Excessive protein can harm the kidneys and liver, as well as disturb the acid-base balance in the body," Li told China Daily. "So FIT acts as a messenger that sends a signal to the brain telling it to stop eating protein."

She said the discovery shows for the first time that even small organisms have the ability to maintain a balance of proteins, fats and carbohydrates in the body through nutrient sensing and regulation.

"Scientists have long studied the biological signals that give organisms an appetite, but little is known about the satiety signals that prevent overeating," she said.

"In humans, proteins give the strongest feeling of being full. The discovery of protein-specific satiety signals could be a new step in unraveling the feeding mechanism that animals have developed."

Although her team's findings are applicable only to fruit flies, Li said chances are high that a similar mechanism is present in mammals, including humans.

She suggested more research is needed on higher-level mammals, like chimpanzees or even humans, to track the circulation of FIT and find out how the regulatory signal reaches the central nervous system and is processed.

"In today's world, obesity has become a major health problem, and a major contributor is unhealthy eating habits and diets," Li said.

Understanding our eating behavior at the biophysical level could help people make healthier diet plans, design personalized dietary medicines, and live healthier lives, she added.