Diet foods for children may inadvertently lead to overeating and obesity, say researchers.
High calorie foods should be eaten in moderation
In tests on young rats, animals given low-calorie versions of foods were induced to overeat, whether they were lean or obese.
The researchers believe low-calorie versions of usually high-calorie foods disrupt the body's ability to use taste to regulate calorific intake.
The University of Alberta study appears in the journal Obesity.
Lead researcher Professor David Pierce said: "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."
The researchers found that young rats given low-calorie foods began to overeat during their regular meals.
However, older, adolescent rats also fed diet foods did not show the same tendency to overeat.
The researchers believe the older rats did not overeat because they, unlike the younger rats, were able to rely on a variety of taste-related cues to correctly assess the energy value of their food.
In contrast the younger animals learned to match tastes usually associated with food high in calories with low-fat alternatives, and so carried on eating to try to get their calorie count up when in fact it had already reached a healthy level.
Professor Pierce said the research underlined the importance of promoting a balanced diet and exercise as the best ways to keep children fit and healthy.
He said: "Diet foods are probably not a good idea for growing youngsters."
Obesity is a significant risk factor for both type-2 diabetes and cardiovascular disease, and soaring rates are posing an increasing public health problem.
Dr Colin Waine, chairman of the UK National Obesity Forum, sounded a note of caution about extrapolating from rats to humans.
But he said: "It is an interesting theory, especially with the amount of low calorie foods which are around now.
"It reinforces the need to try to teach children healthy eating habits from early in life."