March 26 (HealthDay News) -- Fattening foods taste good, but a new study suggests you might also like them because you subconsciously realize they're full of calories.

Scientists report that mice without a sense of taste still developed a preference for sugar water compared to ordinary water. The finding suggests the mice had a way of sensing that the sugar water had calories -- energy for their bodies -- and the other water didn't.

Humans, of course, could be different.

Still, it indicates that "taste isn't the only reason we like high-calorie foods," said study author Ivan E. de Araujo. "Even in the complete absence of taste, it's possible to develop a preference for high-calorie foods."

De Araujo, an assistant fellow at The John B. Pierce Laboratory at Yale University in New Haven, Conn., and his colleagues at Duke University reported their findings in the March 27 issue of Neuron. De Araujo was at Duke when the research was conducted.

The "reward systems" in the brain tell people when they're enjoying things like sex or food. The question for the researchers, de Araujo said, was whether the systems would work without taste as part of the equation.

The researchers genetically engineered mice to not have a sense of taste and then allowed them to drink either sugar water or regular water. To the mice, the two different types of water tasted exactly the same.

But the researchers found that the mice still preferred the sugar water, apparently because they were able to sense that it provided calories and, therefore, energy.

"The brain systems that encode rewards will develop a preference for caloric food even in the absence of taste information," de Araujo said.

If that translates to humans, the findings could explain why some low-calorie foods aren't popular among people even if they don't taste that bad, he said. It's possible that we have a "biological mechanism that reinforces ingestion of high-calorie foods."

The next step in research is to "understand which signals are telling the brain's reward system that something has changed metabolically," he said. "When we ingest calories, we are changing our metabolism."

Anthony Sclafani, a researcher at the Brooklyn College of the City University of New York, said the findings are important, because they're the "first to show that nutrients in the gut can directly activate the brain reward system."

The results still need to be confirmed, said Sclafani, a professor of psychology who studies how the body interacts with food.

He added that the findings could lead to better understanding of artificial sweeteners, which are "are sweet in the mouth but, unlike sugars, do not act in the gut to reinforce food preferences."

However, "even if sugars and artificial sweeteners in the mouth and gut activate brain-reward systems in humans, the implications for human feeding behavior and disorders are not certain at this time," he said. "What is certain is that more research is needed to know the impact on human feeding behavior and to exploit this new knowledge in the clinical treatment of obesity and eating disorders."

SOURCES: Ivan E. de Araujo, D.Phil., assistant fellow, The John B. Pierce Laboratory, Yale University, New Haven, Conn.; Anthony Sclafani, Ph.D., distinguished professor, Department of Psychology, Brooklyn College of City University of New York; March 27, 2008, Neuron