Weight gain has basically happened across the whole developed world because cost per calorie has gotten so low that people just eat more calories on average. This is why semi-glutides are the first thing ever to reduce weight gain and actually make people lose weight because they encourage reduced consumption.

Don't need ultra-processed food to be unhealthy. Rich guys in the 1800s would get fat and get gout and all these issues from overconsumption. It's just they were the only ones who could back then.