Another study finds that high consumption of soft drinks and other sweetened beverages contributes to obesity. But this study, conducted in mice, suggests that one form of natural sweetener -- fructose -- may be especially likely to encourage weight gain.

In the study, researchers at the University of Cincinnati allowed mice to freely consume either plain water or fructose-sweetened water and soft drinks.

The mice that drank the fructose-sweetened water and soft drinks gained weight, even though they took in fewer calories from solid food.

By the end of the study, the mice that consumed fructose-sweetened beverages had 90 percent more body fat than the mice that consumed water only.

The findings suggest that the total amount of calories consumed when someone includes fructose in their diets may not be the only cause of weight gain. Consuming fructose may actually affect metabolism in a way that leads to more fat storage, at least in mice, the researchers said.

"Our study shows how fat mass increases as a direct consequence of soft drink consumption," study author Dr. Matthias Tschop, associate professor in the University of Cincinnati's psychiatry department and a member of the Obesity Research Center at the university's Genome Research Institute, said in a prepared statement.

"We were surprised to see that mice actually ate less when exposed to fructose-sweetened beverages, and therefore didn't consume more overall calories. Nevertheless, they gained significantly more body fat within a few weeks," Tschop said.

The study appears in the July issue of the journal Obesity Research.