Definition of "junk food" also varies a lot. For example, many people have no idea that white bread has a higher glycemic index than sugar itself. So except for the very limited nutritional value of it, it's actually worse than just eating spoons full of sugar. So it passes the definition of "junk food", because hey it's not processed, and it's done in a bakery, traditional right? (not saying it's your case - in general) even though it's as junkier as it gets.
It's possible some people do actually eat healthy and still get very unlucky. But I bet a lot of what many consider healthy isn't. Also, we don't know what we don't know. People didn't know about lead poisoning was a problem until they did. I wonder how many unhealhty stuff we do/consume that passes totally invisible in front of our eyes. The type of things future generations will look back and say "no wonder those people were dying so young of cardiovascular diseases and cancer they were doing X! And get this, they even thought it was healthy/they didn't even know about it!"
