There's no question (statistics-wise) that there is an obesity epidemic, and I think there are two main causes for it:
1. Stress. People who are stressed can have overwhelming food cravings because the stress response involves the body's needing fat and/or sugar in order to calm down and get out of the stress response mode. It's a physical thing, not an emotional thing (like "thinking food equals love"). There's plenty of information out there in reliable sources that explains how food cravings happen as a result of stress. As far as children go, they live under more stress these days too, for any number of reasons (being expected to deal with grown-up stuff too soon, divorce, issues with the school environment, etc. etc.).
I think, related to the cravings matter, that one thing some people may do (besides just giving into the cravings in order to be able to function well) is try not to give into the cravings; so they'll stay away from the "bad" foods. As a result, they keep having the cravings and keep eating more and more "not-so-bad" foods in order to feel better.
2. Too little exercise. There's no doubt about it that a lot of people don't get very much physical activity these days.