There is much greater consumption of processed food today than 30 years ago. "Food science" wasn't so clever back then, so the boxed and premade foods were not

There is much greater consumption of processed food today than 30 years ago. "Food science" wasn't so clever back then, so the boxed and premade foods were not especially tasty. Now they can be addictively tasty. And in these busy times with lots of things grabbing our attention, premade foods - even ones which would appear to be made up of all good ingredients - are the easy choice. To give processed foods a longer shelf life, they need more salt; but to compensate and make them palatable they then need more sugar. So even ignoring the less clear downsides of how processing might affect the chemistry, the simple observation is that foods have more added sugar or sweeteners now than ever before. In human history, that's a pretty rapid and significant change... much like the body shape changes that have occurred during the same 30 years.