Like Lynne said, babies come in all shapes and sizes, and so much of it is out of our control. The best thing you can do is make sure he eats healthy, nutritious food to make his calories count. Some foods are rich in healthy fats, like avocado, egg yolk, cheese, meat, and full fat yogurt. These are all okay for your baby to eat now. After his first birthday, he can start eating peanut butter and whole milk, two more good foods.
My DS has always been tall and skinny and probably always will be, since that's how DH and I are built. That's just the way he is!
