To be honest, these three foods are not very suitable for losing weight. You have to choose a potato, but you must cook it (this calorie is the lowest, a medium-sized potato has about 40 calories after cooking, but an apple has 80 calories and a small sweet potato is close to 100 calories). You can't use any seasoning, and you can't use it with staple food. Sweet potatoes and apples contain too much sugar. Have fun.