Which foods can i eat to gain healthy weight to gain mass?

Calories + protein: The addition of calorie dense foods such as nuts, whole grain pastas, raisins, whole milk, pure fruit juices, butter, avocado, and complex carbohydrates is a healthy way to add more calories to your diet. Lean proteins are also important. Exercising to build muscle mass will increase weight and metabolism, and improve overall mood and health. Good luck!