Sara Kirk of Dalhousie's School of Health Services Administration, in Nova Scotia, said daily life has changed so dramatically in the past 50 years that most people have little opportunity for built-in activity.

"In my research I'm trying to understand what it's like for the person who has a problem to go to a doctor and then be told it's your own fault -- just eat less and do more activity -- because that's how we treat obesity," Kirk said in a statement. "But we must also recognize that there are other things at the core, our policies need to change."

Kirk used global positioning systems to understand how children interact with their environment and explored the intersection of community planning, physical activity and body weight.

"We need to look at the politics around how we price, package and market food," Kirk said. "We need the policy to change, like agricultural policy. For instance, corn syrup is in pretty much everything, because it's cheap to produce."