NEW YORK (Reuters Health) - The diet sodas and snacks so popular with weight-conscious adults may backfire in children, if new animal research is correct.

In experiments with juvenile rats, researchers at the University of Alberta in Canada found that animals that became used to diet foods tended to overeat during meals of regular-calorie animal chow.

This was true for normal-weight and obese rat pups, the researchers found. However, diet foods did not appear to have an overeating effect in adolescent rats.

This suggests that the foods have some unique effect in young animals, and possibly children, the study authors report in the journal Obesity.

They suspect that diet foods disrupted the young animals' ability to learn how various flavors correlate with calories. When they associate tastes, such as sweet or salty, with few calories, even a rich dessert may fail to fill them up as it otherwise would.

It's possible that children given artificially low-calorie snacks and diet sodas might not learn to properly regulate their food intake, according to lead study author Dr. W. David Pierce.

"One thing is clear at this point," he said in a statement. "Young animals and perhaps children can be made to overeat when calorie-wise foods are offered on a daily basis, subverting the body's energy-balance system."

He and his colleagues recommend that parents give their children a well-balanced diet of foods in their natural form, including naturally low-calorie foods like fruits and vegetables.

The findings are based on a series of experiments with young rats, both normal, lean animals and those genetically prone to obesity. Over 16 days, the animals were regularly given gelatin cubes that contained starch, as well as a starch-free "diet" version of the snack.

For some animals, the starchy cubes were flavored with an artificial sweetener and the diet version was flavored with a salty solution. These flavors were reversed for other animals.

After 16 days of this taste training, the researchers gave all the animals a high-calorie snack dipped in either artificial sweetener or a salty solution. They then gave the rats a meal of their regular chow.

Pierce's team found that the animals tended to overeat during the meal if their pre-meal snack had been dipped in a flavor they'd learn to associate with a low-calorie food -- despite the snack's actual high calorie content.

The phenomenon was seen in both lean and obesity-prone rat pups, but the heavier animals generally ate more than their normal-weight counterparts, the researchers point out.

So it's possible, they say, that diet foods could be especially detrimental in the children already at the greatest risk of long-term weight problems.

SOURCE: Obesity, August 2007.