Scientists in Japan have identified a molecule responsible for making mammals feel full, a discovery that could lead to new ways to treat obesity in humans.

Scientists believe appetite is controlled in a region of the brain called the hypothalamus, and the group of researchers claims to be the first to pinpoint an agent that triggers an increase or decrease in appetite.

In an article published on Sunday in the online version of the journal Nature, the scientists identified the molecule as nesfatin-1, which is produced naturally in the brain.

After injecting the molecule into the brains of rats, the rodents began to eat less and lose weight. The researchers also were able to induce the rats to eat more, by blocking nesfatin-1.

“After we injected anti-nesfatin-1 antibody, these rats showed increased appetite and finally showed a progressive increase in body weight,” Dr. Masatomo Mori of the medicine and molecular science department at Gunma University Graduate School of Medicine told Reuters in a telephone interview.

Mori said the finding could pave the way for treating obesity, which has become a major health problem in the developing world as well as in economically advanced countries.

There are at least one billion overweight adults across the world, 300 million of them considered obese, according to the World Health Organization.

Obesity has been linked to chronic diseases, such as type 2 diabetes, cardiovascular disease, hypertension and stroke, and some forms of cancer.