A sweetener commonly used in soft drinks and other foods may lead to more body fat than drinks sweetened with plain sugar.

A new study suggests that fructose may alter the body's metabolism in a way that prompts it to store body fat.

Researchers say the findings may help explain the recently established link between rising soft drink popularity and obesity rates in the U.S. and other parts of the world.

"Our study shows how fat mass increases as a direct consequence of soft drink consumption," says researcher Matthias Tschöp, MD, associate professor of psychiatry at the University of Cincinnati, in a news release.

Fructose is a sweetener found naturally in fruits and honey and is widely used as a sweetener in soft drinks, fruit juices, and cereal. In soft drinks, fructose is usually found in the form of high-fructose corn syrup, which contains 55 percent fructose.

Read WebMD's "Soft Drinks: Scapegoat for Kids' Obesity?"

Fructose: Stealth Fat Builder?

In the study, researchers compared the effects of feeding mice fructose-sweetened water, a soft drink sweetened with sucrose (table sugar), a diet soft drink, or water. The mice were allowed to drink as much as they wanted of their designated beverage.

The mice that drank the fructose-sweetened water gained significantly more body fat than the others, even though they decreased the amount of calories they ate from solid food.

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

Read WebMD's "Sipping Soda Through a Straw May Cut Cavities"

More Weight, More Body Fat

All of the mice weighed about 39 grams at the start of the study. Those that drank the fructose-sweetened water gained an average of 8 grams during the course of the study compared with average weight gains of less than 5 grams among the others.

The fructose-drinking mice also gained more body fat. Body fat increased by nearly 11 percent in the fructose group of mice -- significantly more than the 5 percent increase in the water group. Body fat increased by 7 percent to 8 percent in the soft drink and diet soft drink groups.

Researchers say the results suggest that the body metabolizes fructose differently than other sweeteners or carbohydrates and in a way that favors fat storage.

Their findings appear in the current issue of Obesity Research.

A 2004 report showed that Americans eat 132 calories each day of high-fructose corn syrup and that the figure is closer to 300 calories for the top 20 percent of Americans.

WebMD spoke to study researcher George A. Bray when that study was released.

Bray said between 1970 and 1990, high-fructose corn syrup consumption increased by more than 1,000 percent, largely because the nation's soft drink manufacturers switched from sucrose to high-fructose corn syrup.

Read WebMD's "Drink More Diet Soda, Gain More Weight?"

By Jennifer Warner, reviewed by Michael W. Smith, MD

SOURCES: Jurgens, H. Obesity Research, July 2005; vol 13: 1146-1156. News release, University of Cincinnati.