Childhood obesity, what should be done?

I have two little girls (ages 2 years and 1 year) and neither are over weight and both enjoy a healthy diet with fresh food and fresh fruits. My 2 year old has never eaten crisps, jelly sweets or had a soft drink (only fruit juice) although she has had the occasional chocolate on. Anyway, childhood obesity levels are on the increase and I wondered what other mums/dads thought about this. Personally I think it's the parents to blame after all, we are the ones that supply the food for our children. I have seen so many fat children recently and I know that some cases are due to an illness but not all. I saw a child about six the other day who had bigger than me and she was tucking into a tub of ice cream, the father being overweight too. If i saw my children starting to put weight on then i would take drastic action before they got overweight. What would you do and what do you think is to blame for this "new epidemic"?