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Do Sweeteners in Diet Soda Increase Weight?

Rat Study Links Weight Gain to Low-Calorie Sweeteners; Critics Say No Relevance for Humans
WebMD Health News
Reviewed by Louise Chang, MD

Feb. 11, 2008 -- It may sound counterintuitive, but replacing the sugar in diet sodas and other foods with reduced- and no-calorie sweeteners may make weight control harder, a small animal study shows.

Rats in the Purdue University study that were fed regular feed and yogurt sweetened with no-calorie saccharin took in more total calories and gained more weight than rats fed regular feed and yogurt sweetened with sugar.

Researchers speculate that over time, reduced-calorie sweeteners like saccharin, aspartame, and sucralose condition the body to no longer associate sweetness with calories, thereby disrupting its ability to accurately assess caloric intake.

This disruption may, in turn, lead to overeating, they note.

"If this is the case in rats, there is little reason to think that humans don't have this same response," researcher Susan Swithers, PhD tells WebMD. "It is possible that consuming these products interferes with one of the mechanisms that helps to regulate weight."

She adds that this could help explain why the dramatic rise in obesity has occurred at the same time that sales of diet sodas and other products containing low-calorie sweeteners have skyrocketed.

(Do you use artificial sweeteners as part of your diet? Tell us about it on WebMD's Dieting Club: 25 – 50 Lbs to Lose message board.)

Industry Response

But a spokeswoman for the low-calorie sweetener industry was highly critical of the research, noting that the study involved just 27 rats.

"I think studies like this are a disservice to the consumer because they oversimplify the causes of obesity," registered dietitian Beth Hubrich of the Calorie Control Council tells WebMD.

"It is true that there has been an increase in the use of low-calorie sweeteners at the same time that we have seen an increase in obesity, but there has also been an increase in the use of cell phones and nobody is suggesting that they are causing obesity."

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