Eat in a consistent calorie surplus every day
Increase portion sizes at each meal
Eat more frequently if large meals are hard
Choose calorie-dense foods like nuts, nut butters, avocado, olive oil, cheese, whole milk, rice, pasta, and dried fruit
Add liquid calories with smoothies, milkshakes, and meal replacement drinks
Include protein at every meal
Prioritize strength training to build muscle
Reduce excessive cardio if gaining weight is difficult
Track body weight weekly
Track calorie intake to ensure you are actually eating enough
Sleep enough each night
Manage stress to avoid appetite loss
Eat before and after workouts
Use snacks between meals
Avoid filling up on low-calorie foods and drinks
Be consistent for several weeks before adjusting intake
Consult a doctor or dietitian if weight gain is unexpectedly difficult