Throughout the time my older brother was growing up, he was always a head taller than the rest of the class, and thin. When he was taken to the doctor for a checkup, the doctor would tell our mother, "He's underweight. You need to feed him more."
My mother replied, "He eats breakfast. He has a peanut butter and jelly sandwich. Then he eats lunch, and then a peanut butter sandwich. He eats dinner. How much more can I feed him?"