The peel and the pith (white spongy part around the flesh) of an orange are pretty useful than we realise. Studies show that the rich nutrients present in the pith help lower cholesterol, reduce blood pressure and inflammation. Also, pectin (present in both peel and pith) suppresses hunger. You can use leftover orange peel to zest up your meals, toss into smoothies or put in baked goods.
Apple skin has slightly more nutrition than the flesh. The nutrients present in the skin helps remove toxins and waste from the body, and clean out the digestive system. It also helps reduce body inflammation.