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If you're trying to lose weight, you may want to skip the diet pop and go straight for the sugar.

A new study has found that consuming artificial sweeteners makes it harder to limit food intake and keep weight off.

In a study of two groups of rats, researchers at Purdue University found those fed yogurt sweetened with saccharin, a zero-calorie sweetener, ate more and gained more weight than those that ate the same food containing sugar.

The results, published today in the American Psychological Association's Behavioral Neuroscience journal, are the latest to link artificial sweeteners and obesity.

Although more research is needed to determine whether the same is true for humans, researchers said it is possible that artificial sweeteners confuse the body's natural attempt to keep track of calories based on the sweetness of the food being consumed.

"I think at this point the issue is just that these kinds of products are not necessarily going to just produce weight loss. This suggests that it may actually produce the opposite effect," said Susan Swithers, an associate professor in the department of psychological sciences at Purdue University and one of the study's authors.

Dr. Swithers has been studying the effect sugar and artificial sweeteners have on a rat's diet for several years. She co-authored a 2004 study suggesting rats that consumed sugar substitutes have greater difficulty counting calories.

Researchers used saccharin in this new study, but Dr. Swithers said she believes the results could also apply to other artificial sweeteners common in many foods. Saccharin is banned in Canada because of concerns it may be linked to health problems, but officials are reviewing those restrictions in light of new scientific evidence showing it may not be harmful to humans.

The new findings are consistent with other studies involving humans that have raised the possibility that "increased intake of no-calorie sugar substitutes could promote increased intake and body weight gain," the study says.

For instance, research published last year by the Framingham Heart Study found that people who drank one or more cans of pop a day, regardless of whether it was diet, were 48 per cent more likely to suffer from obesity and other health problems.

In response to the new study, the Calorie Control Council, a U.S.-based industry association that represents companies that sell artificial sweeteners, said the research oversimplifies the complex issues that contribute to obesity among humans and several studies have demonstrated that artificial sweeteners can help with weight loss.

"Although they are not magic bullets, low-calorie sweeteners in beverages and foods can help people reduce their calorie [energy] intakes," the council said in a statement.

But in their study, the Purdue researchers pointed to significant instances that highlight how artificial sweeteners may change the body's response to food and may distort the ability to control calorie consumption.

Rats that consumed food sweetened with saccharin ate more and didn't later compensate by cutting back on the amount they ate. Although all of the rats had similar weights at the start of the experiment, those that ate food containing the sugar substitute "gained significantly more weight" than those who ate sugar.

The researchers made another revealing discovery when they examined the body temperature of the rats when they ate.

Body temperature typically rises after eating, but researchers said rats that had become accustomed to consuming the artificial sweetener didn't have a significant temperature change. They suspect that could mean the rats' appetite control mechanisms were disrupted when they consumed the artificial sweetener, which may have led to overeating.

"[People] may want to simply consider the possibility that simply switching to use these products isn't automatically going to result in dramatic weight loss," Dr. Swithers said.