There are studies that have INDICATED the use of high fructose corn syrup as well with other sweeteners has been a factor. But to what extent hasn't been proven, certainly not that they're the sole cause, which of course, they are not.
Highly processed foods are an even bigger contributor. Not only readily available, but cheaper as well as easier to prepare, again, thanks to subsidies. This is why eating a can a Chef Boyardee for dinner is more likely if you're living in a ghetto than it is buying healthy fresh organic food items and making dinner for yourself. I know, I did that for 21 years. Stock up on that or Campbell's Chunky Soups when they're on sale and whatnot, and voila, dinner is half a day on the pilot on the stove away.
A decrease in physical activities also a factor. There was a time that work was actually work, not sitting in a cubicle all day fiddling on social media. Now labor that involves real labor is reserved for legal aliens. Even children don't play outside anymore. Xbox all day not playing.
High fructose corn syrup is also a consequence of farm subsidies. Corn is a horrible crop to grow - high maintenance, requires a lot of fertilizer, pesticides, herbicides, and lots and lots of water. But it is a very high yield crop with a lot of potential uses. There would be no profit in growing corn if it wasn't for it farm subsidies, at least on a mass scale that it is normally grown and in most areas. The cost of growing corn far exceeds the profit that is made from selling it or its products.