Looking at the aspects of weight gain, but especially a healthy weight gain, it is always useful to rely on foods rich in nutrients and calories. It will not promote muscle gain or good health if one just consumes any junk foods including fast foods and other calorie-rich foods. Instead, an optimal plan is to take such foods that contain all the right elements for muscle building, such as healthy fat, whey protein and carbohydrates . If you are one of them and you want to pile on the muscle mass, then here are five foods that are high in calories.