We are what we eat....I don't think profit for the food giants is making us fat, we make the choices
Profit? I'd say this all begins with education, adults can educate themselves but changing habits is hard, so that journey will have to start with our kids both at home and at school, educating kids about food and giving them things that are NOT bad for them and having them taste a wide variety of foods to they develop a palate and know there are many options to work with and create nice dishes.
My 4 year old loves greens, olives and olive oil (dipping some nice artisanal bread in a good extravirgine is one his favorites), eats smelly artisanal cheeses, he also favors water as drink simply because we consistently gave him water rather than juice or anything else..
The problem is, there are many places where its significantly less economical to eat healthy unprocessed foods. Food giants have something to do with that. People like me, who have a decent salary, live in a middle or upper middle income neighborhood, can afford in both time and money fresh foods make the choice to be healthy everyday. I choose to eat nutritious food or fast food. If I choose to eat unhealthy, I choose whether to not to exercise extra to try and mitigate some of that. My parents had the resources to introduce me to different foods and expand my palate as a kid. My income and circumstances I was born into allow me that choice.
However, if you live in a food desert and/or make significantly less than the average income, eating habits are much less a choice. In those areas, grocery stores have higher prices for produce, often times than even a upper end store like Whole Foods, for much less quality. At the same time big agri is one of the most subsidized industries, and the crops that get subsidies tend to be cereal grains used to make either high sugar foods OR go into animal feed, which in turn subsidizes red meat. These in turn get combined to make things like a Big Mac,, with high salt, high fat from the subsidized meat and cheese, and often deceptively high amounts of sugar from sauces. High salt, fat, and sugar contents are also addictive to our brains.
A child brought up in that environment, is very likely, even if they can escape it economically as an adult to have their brain chemistry tied to it. Parents in that environment are both less likely to have the resources to cook for their kids, and the time. That's not to say personal responsibility plays no role. I very much believe it does, and we have an ethical obligation to try and fix things we can control, even when dealt a bad hand. But I think it'd be naive not to acknowledge for a very large portion of the American population (and probably many others), our food system stacks the deck against them being healthy. Some will overcome it, many won't.