system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why are we set up to not eat healthy?

In America, there was an obesity scare in the 1970's-1980's that told Americans "fat is bad" and so they've removed the fat content from many foods. by doing that, they became less tasteful and so to replace that they added sugar. 

But also, we've been told every day to eat our grains and oats. But the thing is, most of the bread that we consume is actually really bad for us, even the whole-grain breads. It isn't the same oats and grains are grandparents consumed.

Many companies too try really hard to make things seem healthy when they aren't. 

So how is a person in this society supposed to be able to eat healthy? Do you have any tips and tricks to make it simple? Can you point us to sources we as consumers should be able to trust?
gpt
If by "set up" you mean biologically it's because some nutrients were much rarer then others and over time we became hardwired to seek those particular nutrients more so over others since obtaining those nutrients required more effort. Now in modern times those nutrients are quite abundant but we still retain that need to seek those once rare nutrients which causes problems due to excess. Also those rare nutrients: salts, sugars, fats, etc. are not unhealthy.