Some packaged foods—like yogurt or bagged greens—are "clean." To pick healthy processed foods, look for whole foods in ingredient lists. If an ingredient sounds suited for a chemical lab, think twice. Another benefit to limiting processed food: in a study in Food & Nutrition Research, people who ate a "whole food" sandwich (Cheddar on multigrain bread) burned about 64 more calories per meal than those who ate a "processed" sandwich (processed cheese on white bread). The energy needed to digest a less-refined, more nutrient-dense sandwich may explain the extra calorie burn.