The change was far too rapid for anything else to be remotely the primary cause.
If you put a past heroin addict locked in a room with unlimited heroin readily available, chances are likely 9 times out of 10 that person is going to partake eventually. Same goes for our food environment and way of life.
You see, companies have a way of stopping that and it only costs millions. They pay off the politicians and the politicians say that companies have more freedoms than individuals.
Sickness and obesity is much better business. Fitness, medical and fast food industry combined are trillions of dollars.