While that may be true, i think the main reason for obesity is not diet, but overeating.
Eating is one of the top reactions of human body to stress. It helps the person cope up with stress.
Modern society is living restricted, over-stressful lives in current system. Leave aside working like slaves to make ends meet, there is no security of future. Which is one of the top reasons for stress.
This is not too different for the young too - just because someone is a teenager and even 'unaware' of many things in society yet, does not mean that person does not have a subconscious understanding of the future lying ahead of them. They see people around, their relatives, neighbors, acquaintances trying to get by in life, everyone struggling.
Even in the case of fairly 'privileged' classes its not so different, even upper middle class doesnt have security of their future as they used to.
