Who/What is to blame for modern epidemics of obiesity?

Epidemic of obesity is more and more frequent among people. What causes that? In my opinion it's because of the luxury. Developing technology made our life easier. We use cars instead of a walk or  a bike. Children play computer games all the time instead of outdoor activities. We don't even go to do shopping, we just do it through the internet without moving from our seat. Widely available sweets make us even fatter. All of these things are side effects of the luxury and innovation which should help us but if we won't use them wisely, obesity will be more common.