Fewer than 10 percent of children in primary school manage to average half an hour exercise a day. Among teenagers, it is fewer than 30 percent.
As a result, by 2015 one Dutch child in five will be too heavy, Nicis found.
The institute found a direct relation between weight gain and the opportunity to play games or sports in the areas where children live.
Nicis underlined the duty of town and city councils to develop opportunities for exercise, by encouraging children to bicycle to school and improving safety at sports fields so children are not deterred by the risk of being attacked.
The institute also stressed that parental attitudes were a determining factor: sporty parents tend to have sporty children while lazy couch-potatoes have children like them.