With what foods can a vegetarian have to gain back healthy weight?

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. Proteins are also important. Exercising to build muscle mass will increase weight and metabolism, and improve overall mood and health. Good luck!