The study -- Sport, Physical activity and Eating behavior: Environmental Determinants in Young people, or SPEEDY -- was coordinated by Esther van Sluijs, who led a team of researchers from The Medical Research Council Epidemiology Unit and The University of East Anglia, in Norwich, England.

During the summer of 2007, the team studied the diet, physical activity and body shape of 2,064 students ages 9-10 in 92 schools in the county of Norfolk. They also investigated their socioeconomic and ethnic backgrounds as well as school and home neighborhood environments.

"To date, the extent of the problem of physical inactivity and unhealthy dietary habits in children has been largely unknown," van Sluijs said in a statement.

"Good data about physical activity, assessed using valid and reliable measures in large samples, are scarce -- especially in children."

The study, published in journal BMC Public Health, found two-thirds of children adhere to the physical activity guideline of at least 60 minutes of moderate-to-vigorous physical activity each day, but daily consumption of fruit or of vegetables was reported by some 50 percent of the children.