Study questions saccharin benefits

Casting doubt on the benefit of low-calorie sweeteners, new research released Sunday reported that rats on diets containing saccharin gained more weight than rats given sugary food.

The study in the journal Behavioral Neuroscience found that the artificial sweetener appeared to break the physiological connection between sweet tastes and calories, driving the rats to overeat.

Lyn M. Steffen, an associate professor of epidemiology at the University of Minnesota, who was not involved in the report, said the study offers a possible explanation for the unexpected association between obesity and diet soda found in recent human studies.

Researchers have puzzled over whether diet soda was a marker for poor eating habits, or whether the ingredients in diet soda caused people to put on pounds, she said.

"This rat study suggests a component of the artificial sweetener may be responsible for the weight gain," Steffen said.

Steffen's research, published last month in Circulation: Journal of the American Heart Association, showed that people who drank diet soda had a higher risk of developing metabolic syndrome, a cluster of symptoms that includes obesity, than people who drank regular soda.

The food and beverage industries rejected the report.

"The causes of obesity are multifactorial," said Beth Hubrich, a dietitian with the Calorie Council, which represents low- and reduced-calorie food and beverage marketers. "Although surveys have shown that there has been an increase in the use of 'sugar-free' foods over the years, portion sizes of foods have also increased, physical activity has decreased and overall calorie intake has increased."

The number of Americans who consume sodas and other products containing sugar-free sweeteners more than doubled to 160 million in 2000 from fewer than 70 million in 1987, according to the report.

Over the same period, the incidence of obesity among U.S. adults rose to 30 percent from 15 percent. One interpretation of the trends is that people have been turning to lower-calorie foods to control an increasing problem with weight gain.

An alternative interpretation is that artificial sweeteners lead to biological or behavioral changes that cause people to eat more.

This possibility is easier to test in rats than in people because scientists can control the animals' diets and measure exactly what they eat, said the report.

In the experiment, funded by the National Institutes of Health and Purdue, nine rats received yogurt sweetened with saccharin and eight rats received yogurt sweetened with glucose, which is close in composition to table sugar. After receiving their yogurt snack, the animals were given their usual rat chow.

At the end of five weeks, rats that had been fed sugar-free yogurt gained an average of 88 grams compared to 72 grams for rats that dined on glucose-sweetened yogurt, a difference of about 20 percent. Rats fed sugar-free yogurt were consuming more calories and had 5 percent more body fat.