Don't most people know the theory behind a healthy lifestyle?
The way we live today is to blame for much obesity, and not ignorance. We sit far too much and drive rather than walk.
I was brought up on stodgy, filling food..pastry, potatoes, suet puddings etc, as was the generation before me. Like many of us growing up money was tight and bread and jam, bread and dripping etc, were our snacks. However, we didn't get fat and the generation before us and ours are living long lives. The difference is movement. Everything we ate we played off or worked off. We walked everywhere. Work was more labour intensive. The minute my life became more sedentary, through chronic conditions and ill health, I gained weight despite a reasonably healthy diet.
I brought my children up to eat healthily and I am so glad they just missed out on being the generation that used screens for amusement. They also walked to and from school. I used buses to get to work as well as much walking.
Fast foods are the easy option. Eating out has become the norm for many. I can't see the clock being turned back.
It's easy to make soup and it's not much harder to peel veg than open a can but time, lifestyle and habit have taken hold. I hate to see podgy children. There is no need for it but their parents are also victims of modern life.
We must remember too that weight gain and being seen as a couch potato can lead to a cycle of depression and when people lose hope and faith in themselves, food, ironically, can become a crutch.