Question: how to gain weight by vegetarian diet?
Answer: Nuts and Nut Butters. Nuts are a great source of protein, healthy fats and calories, making them an excellent choice if you're looking to gain weight. ... 
Avocado. ... 
Quinoa. ... 
Tahini. ... 
Olive Oil. ... 
Dried Fruit. ... 
Legumes. ... 
Sweet Potatoes.