The obese individual is responsible for obesity. Fast food chains and restaurants do not force feed their customers. Parents are responsible for making their children obese as they have the power to arrange what is eaten. If there is an appetite for anything, however harmful, there will always be companies ready to supply it. There's a love of fast food - it's convenient, it's tasty. So there are fast food suppliers. Don't blame them for people who use them too much.
Fast food restaurants should not bear the entire responsibility for the obesity crisis in the world, but they certainly play a role. The amount of responsibility that the fast food chains should accept may differ according to different people. People have the responsibility themselves to determine what food they are going to put into their bodies. However, it doesn’t help that there are ads everywhere showing delicious unhealthy foods.
They are also rather cheap. Fast food restaurants do not offer as many healthy items as they do unhealthy items. These unhealthy items are usually cheaper and easier to eat for those people who like to eat on the run. Nowadays, some fast food chains are offering a few more healthy items to their menus.