I’m always looking to add protein to my day. Why? Protein is a nutrient that not only helps build muscle but also helps keep me full so I don’t get "hangry." (And my boyfriend doesn't like it when I get "hangry!") Some of my favorites are plain low-fat Greek yogurt, tofu, cheese, and eggs. Want 100 more options?! Get 100 of the Healthiest Foods, Ranked by Protein.