Parents who feed young children low-calorie foods and beverages in a bid to keep them at a healthy weight may inadvertently contribute to overeating and even childhood obesity, new research suggests.

In studies of laboratory rats, researchers at the University of Alberta found that young rodents could be trained to connect the taste of food with their caloric value. When food flavours were associated with low-caloric energy – as with diet foods and drinks – the rodents would chow down on far more food at regular meals than their bodies required.

Calorie-wise foods that taste the same as their full-calorie counterparts may undermine the body's natural ability to regulate food intake and weight, said David Pierce, a professor of sociology and lead author of the study.

He speculated that a similar mechanism could lead young children who consume diet foods and drinks to also end up overeating and gaining excess weight over time.

"I think the data showed that if you subvert the usual relationship between taste and calorie content, it leads to disruption of the normal physiological and behavioural energy balance in juveniles, resulting in an overeating effect," Pierce said Tuesday from Edmonton.

"Based on what we've learned, it is better for children to eat healthy, well-balanced diets with sufficient calories for their daily activities, rather than low-calorie snacks or meals," he said.

For one of the studies in their research paper, published Wednesday in the journal Obesity, four-week-old lab rats were conditioned over 16 days to associate certain sweet or salty flavours with low-calorie food.

Following that conditioning, the rodents were fed a high-calorie rice cake snack dipped in a flavour they'd come to associate with low-energy foods. And even though the rice cake should have helped satiate their need for energy-producing calories, the animals still overate when it came to the regular meal that followed.

In a second study, eight-week-old "adolescent" rats had low-cal foods added to their diet, but those animals did not display the same tendency to overeat. The researchers believe the older rats didn't eat excessively because they had learned as youngsters to rely on a variety of taste-related cues to correctly assess the energy value of their food.

Dr. Katherine Morrison, a pediatric endocrinologist and childhood obesity expert at McMaster University, called the study intriguing.

"I welcome a study such as this to help us to move further in our understanding of how do we become full and what is it that encourages us to eat," Morrison said from Hamilton.

"When it comes specifically to sweetened drinks, I think this study raises a question (about) just substituting diet pop for (regular) pop. It doesn't tell us that we shouldn't do it. It raises the question: Is that a good approach?"

Morrison said she encourages parents when their child comes home ``famished" after school to have healthy foods on hand – such as vegetables, fruits or salad – "that will sort of take the edge off as you move into your evening meal.

"You certainly don't want to be going with something like chips or chocolate bars or even granola bars, which give a pretty high-calorie punch in short order."

Dr. Jean-Pierre Chanoine, head of the endocrinology and diabetes clinic at the B.C. Children's Hospital, said childhood obesity experts often advise that overweight children substitute diet soft drinks for all or most of the regular pop they drink as a way of reducing calories.

But this study suggests that could be a mistake, he said.

"We tell them if you can replace one can of pop with a diet equivalent, you're going to be doing well," Chanoine said from Vancouver. "But maybe we are actually barking up the wrong tree. Maybe we should not say that."