Another way I've heard it stated: "single ingredient foods." And as you prepare them, try to keep them that way.

For example, adding a ton of butter to potatoes makes them 10x less healthy. More or less, calorically they become fries. Fries taste great but they should be an occasional treat, not a staple.

That’s really a question of what the rest of your lifestyle and diet looks like.

Potatoes and butter go really well together because it covers a more complete percentage of our dietary needs. If your diet mostly consists of veggies + starches (rice/potatoes/etc) + ultra lean meats then adding a little butter is actually a good idea. If you’re constantly eating fired chicken then it isn’t.