Though my unheathly relationship with junk food is a process that I am working on, I find that sticking to whole single-ingredient foods for an extended period of time is almost always an excellent choice. Now there is individual variance in all of our bodies and for me personally my body responds well to a lower carbohydrate diet with a lot of emphasis on cultivar vegetables, chicken and beef. Recently I've been experimenting with different types of veggies and switching out beef for seafood like salmon and shrimp. My opinion is to ignore most studies and experiment with foods that improve your energy levels, motility, gut health and sleep. Studies are great for general knowledge but at the end of the day nobody else in the world has your body except you.
(If anyone disagrees I would love to have a friendly discussion on this, I love talking about nutrition!)