When boomers were the age of millennials, they were eating foods that were just foods. They weren't overly engineered. The 80s came about, scientists decided that fat was a problem, and so they started removing fat from food. But in order to make those foods palatable, they needed to add a filler. They chose the cheapest one, most addictive one: sugar. Then when people got tired of eating oat bran with everything, they added the fat back but kept the sugar. So now you've got the very worst of both worlds. Likewise, when boomers were growing up, even the pre-packaged food they ate was packaged in wax paper and glass. Everything today is some form of plastic.

It's much harder to become obese if you aren't eating products that come out of food labs.