Sugar substitutes, often deemed healthier than regular sugar, caused weight gain in rats, according to a Purdue University study.

The artificial sweetener saccharin disrupted rats' ability to manage calories, the study concluded; however, it is too soon to assume that the same result occurs in people.

The study is inconclusive because of the lack of human data, said Chris Fan, a specialist in endocrinology and internal medicine at Hershey Medical Center. But anything that affects weight gain would influence his diabetes patients, he said.

"In many instances, if you give people fat substitutes or sugar substitutes, they do gain weight; they figure they have license to eat more calories," Fan said. "Who knows what a rat or a mouse thinks? Presumably, they're not conscious the way we are."

The study, published in the February issue of Behavioral Neuroscience, was performed by researchers Susan Swithers and Terry Davidson at Purdue University.

"I think the thing that our data suggests is that at least consuming saccharin made it more difficult for the rats to track the other sweet things," said Davidson, a professor of psychology. "We think the principle may apply to both rats and other animals."

In the study, rats who were fed saccharin-sweetened yogurt over a two-week period gained more weight than those who ate yogurt made with glucose, a natural high-calorie sweetener.

Animals are conditioned to associate sweetness with high-calorie content, the study explains, and calorie-free artificial sweeteners interrupt this process, causing us to eat more and gain more weight.

The rats that ate sugar had a higher body temperature at mealtime than those who ate the artificial sweetener because they were preparing to metabolize the calories they consumed, while those who ate the artificial sweetener stored calories, thus gaining weight.

"The other thing we know, too, is while weight is associated with mortality, it's not an absolute cause-effect," Fan said.

Artificial sweeteners, also called sugar substitutes, are used instead of sucrose (table sugar) to sweeten foods and beverages, according to the National Cancer Institute.

Saccharin is most popularly used in Sweet 'N Low, according to the Calorie Control Council, and in soft drinks, candy and other products.

The council indicates that saccharin is safe for humans, and that the average saccharin user ingests less than 1 ounce of the sweetener each year.

"The rats are the best that we can do now in terms of a controlled feeding study," said Dr. Rebecca Corwin, associate professor in nutritional neurosciences.

"We've been able to show correlation in humans, but we've never been able to show causation. And furthermore, I don't know how much of this artificial sweetener the rats consumed and how that translates to how much people consume in a day."

If true for humans, this could pose a problem for students who rely on diet soda or other artificially sweetened beverages for energy.

"I don't really drink soda, [and] I don't really ever use sugar in my coffee," Ian Myers (sophomore-chemical engineering) said.

"I do drink the energy drinks, sugar-free, so I don't crash. I don't drink sugar in my energy drinks just for that."

Amy Hess, a recent Penn State graduate, said she likes sugar substitutes because they taste sweeter than sugar.

"They dissolve better in liquid," Hess said. "I'm mostly motivated by taste."

A 2004 study by the Purdue researchers suggested that rats had more trouble detecting calories in liquids than in solids, which could increase the possibility of gaining weight.

"There's like a psychological feeling that people need to eat more than they think," Lauren Mary Smith (junior-nursing) said, because as people grow up, they are trained to finish all the food on their plates.

Corwin would still recommend artificially sweetened beverages over sugary drinks.

"Maybe consider water or decaf coffee or tea or even fully caffeinated if you want. Maybe you shouldn't be drinking so much of this artificial stuff," she said.

"I think one of the problems is that people are consuming empty calories that aren't necessarily bad, but they occupy a large proportion of the diet. Maybe mom was right: moderation was the way to go."