Time spent in front of the TV as a toddler could lead to a larger waistline and poor sports ability later in childhood, a new study suggests.

The study by researchers at the University of Montreal and Saint-Justine Mother and Child University Hospital found that for every extra hour of TV a child watched at the age of 4 1/2, their waistline increased by slightly less than half a millimetre.

"We already knew that there is an association between preschool television exposure and the body fat of fourth grade children, but this is the first study to describe more precisely what that association represents," study senior author Dr. Linda Pagani said in a release. "Parents were asked about their child's TV habits.

Trained examiners took waist measurements and administered the standing long jump test to measure child muscular fitness. We found, for example, that each weekly hour of TV at 29 months of age corresponds to a decrease of about a third of a centimetre in the distance a child is able to jump."

Researchers examined data for 1,314 children who had taken part in the Quebec Longitudinal Study of Child Development. When the children were 2 1/2 to 4 1/2 years old, their parents reported how many hours of TV they watched during the week and on weekends. The average was 8.8 hours a week at the beginning of the study but increased on average by six hours over the next two years to get to 14.5 hours a week.

"In summary, our findings suggest that as a preferred pastime, television also represents a modifiable lifestyle factor that is associated with later physical prowess and health," the study says.

The finding were published in the International Journal of Behavioral Nutrition and Physical Activity.