What should i do if i want to gain weight fast?

Calorie dense foods: Eat calorie dense foods, such as nuts, peanut butter. If you want to do it the healthy way, add avocado. And healthy oils such as canola and olive oil to your foods. If you want to gain weight fast in an unhealthier way, eat fatty foods- like rib steak, cheese, fried foods, eat snacks in between meals, make high calorie shakes, as snacks.