Dr. Olivier Drouin of Ste. Justine's Hospital says many parents are overly optimistic about their child's risk of picking up unhealthy habits.

He examined cigarette smoking and excessive weight gain, and found that 80 percent of parents do not think their children are at risk.

But the evidence shows that more than 33 percent of children are overweight.

In many cases, parents will not be honest even with doctors who point out their children are unhealthy.

Watch the interview for more.