I mainly feel negatively towards the food industry for this. I mean, if you put a bunch of humans in a place where Cheetos and KFC grew on trees, we'd be having the same problem. This type of food simply shouldn't be consumed as a main source of energy. And the fact is, many humans will inevitably gravitate towards the cheapest and most convenient food source. No amount of cultural enlightenment is going to eradicate this. It'd be wonderful if it could, and if these campaigns for healthier living would convince every person to stop eating badly on their own conscious terms. But right now they're competing with a massive, expensive food industry that makes all of its money from doing the exact opposite. IMO the solution will be in the direction of strengthening awareness of why this food is bad for you, awareness of exactly what the food industry is doing, AND getting everyone on the collective ass of the corporate food giants. Probably disallowing junk food to be bought on food stamps, too. If a company claims to provide food, and all they provide is sneaky snacks that mess with your body's ability to understand what it's actually getting, nutritionally... it's just not right.
I fear that this problem can only be solved by good policy. To me, that means making the incentives to eat healthy outweigh the incentives to eat unhealthy. Namely, it must be relatively cheaper to eat well than to eat shit. The only way this is possible is to overhaul the farm bill, which is at the root of the problem. Unfortunately, Congress is about to reauthorize this travesty, and the only notable 'reform' is to gut SNAP, the one positive in the bill.
That "inevitability" stems in part, from economics and in part, culture. I think that you're right that cultural enlightenment won't fix the problem, at least not without the economic side. Unfortunately, as part of the cultural side (in America most especially) efficiency at the cost of all else is prized, much to our detriment at nearly every level of our society. This means that the people employed to engineer junk food do it well. They do it as efficiently as possible so that their company or corporation can most efficiently make money. Thus lubricated by the warm, lipid embrace of highly engineered foods, many people slip down the long slide toward death. Efficiency and morality are often at odds, because well, doing the right thing is all kinds of inconvenient, time consuming, resource draining. In a word: inefficient.