Christen Smith, RDN, spokesperson for the Academy of Nutrition and Dietetics and registered dietitian for Atlanta-based Piedmont Healthcare says that apples are high in fiber but low in calories and good for those looking to lose weight. In addition, fiber also helps slow digestion and makes you feel full for a longer time. In order to get a better feeling of fullness and optimal fiber intake, you can also eat the skin, reported by the Everyday Health page.