Feb. 11, 2008 -- Calorie-conscious consumers who opt for diet sodas may gain more weight than if they drank sugary drinks because of artificial sweeteners contained in the diet sodas, according to a new study.
A Purdue University study released Sunday in the journal Behavioral Neuroscience reported that rats on diets containing the artificial sweetener saccharin gained more weight than rats given sugary food, casting doubt on the benefits of low-calorie sweeteners.
"There's something about diet foods that changes your metabolic limit, your brain chemistry," said ABC News' medical contributor Dr. Marie Savard.
Though Savard said more research needs to be done to uncover more information, the study does hint at the idea that the sweeteners alter a person's metabolism.
Savard said another recent study, which included more than 18,000 people, found healthy adults who consumed at least one diet drink a day could increase their chance for weight gain.
In the Purdue study, the rats whose diets contained artificial sweeteners appeared to experience a physiological connection between sweet tastes and calories, which drove them to overeat.
"The taste buds taste sweet, but there's no calorie load that comes with it. There's a mismatch here. It seems it changes your brain chemistry in some way," Savard said. "Anything you put in your mouth, your body has a strong reaction to it. It's much more than counting calories. It seems normally with sweet foods that we rev up our metabolism."
The information may come as a surprise to the 59 percent of Americans who consume diet soft drinks, making them the the second-most-popular low-calorie, sugar-free products in the nation, according to a consumer survey from the Calorie Control Council, a nonprofit association that represents the low-calorie and reduced-fat food and beverage industry.
Because so many foods today contain artificial sweeteners, the study results may go beyond diet drinks.
"The truth is, we're putting artificial sweetener in so many different things in water, in yogurt," Savard said. It's unclear if the results only adhere to diet sodas, she said.
"We have to rethink what this artificial stuff does to us. If we put this in water it might not be so good," she added.
The Calorie Control Council issued a statement that disagreed with the findings of the Purdue study and noted that past studies indicated low-calorie sweeteners benefit weight control.
But Savard said people who consume a drink or more a day should think about cutting back their consumption.
"The truth is, if you're consuming a drink or more a day, you know it. You know that you're taking it, and you really have to think about eliminating it. You're probably the very person who needs to change those health behaviors to prevent the diabetes, heart disease and stroke," Savard said.
"If you're just taking it once in a while, fine -- no big deal. If you're consuming one or more drinks a day, you should rethink what you're doing. You might be negating the whole reason in the first place."