Washington (IANS): A single molecule in the intestinal wall, activated by waste products from gut bacteria, plays a key role in determining whether the host animals stay lean or fatty, says the latest research.

When activated, the molecule slows the movement of food through the intestine, allowing the animal to absorb more nutrients and thus gain weight. Without this signal, the animals weigh less.

The research, based on mice studies, shows that the host can use bacterial by-products not only as a source of nutrients, but also as chemical signals to regulate body functions. It also points the way to a potential method of controlling weight, the researchers said.

"It's quite possible that blocking this receptor molecule in the intestine might fight a certain kind of obesity by blocking absorption of energy from the gut," said Masashi Yanagisawa, professor of molecular genetics at University of Texas Southwestern and a senior co-author of the study.

The study appeared online in Proceedings of the National Academy of Sciences.

Humans, like other animals, have a large and varied population of beneficial bacteria that live in the intestines. The bacteria break up large molecules that the host cannot digest. The host in turn absorbs many of the resulting small molecules for energy and nutrients, according to a university press release.

"The number of bacteria in our gut far exceeds the total number of cells in our bodies," said Yanagisawa. "It's truly a mutually beneficial relationship. We provide the bacteria with food, and in return they supply energy and nutrients."