Making homemade protein smoothies can be a healthy and quick way to gain weight. Since commercial versions are often full of sugar and lack nutrients, homemade smoothies are the most popular alternative. If you have lactose intolerance, you can combine both with 2 cups (470 mL) of dairy milk or soy milk. Both have more nutrients and calories than other alternative milks. We feature items that we believe are useful to our readers. We may receive a small commission if you buy through links on this website. Here are 18 of the best foods to help you gain weight or add muscle, the healthy way.