How to bulk up fast? While some are constantly trying to lose excess fat, others find it tough to gain weight. Ironically enough, junk food won’t work for those who can’t gain weight. The solution is simple — eat food rich in healthy fats and protein, like milk, avocados, nuts or salmon. Eating the products on our list as a snack, garnish, or the main dish will help you gain weight. And if you combine them with regular exercise, they will help you to build muscle.