•In simple words, eat more calories than you can burn. •For slow gain eat around 400 calories per day, for fast gain eat around 800 calories per day.
•Gaining weight doesn't mean gaining fat, instead try to gain muscles •Eat protein-rich diet to gain muscles, aim for 1.5-2.2 grams of protein per kilogram of your weight
•To gain weight, eat at least 3 meals per day and make sure to include plenty of fat, carbs, and protein •This will help you to acquire more calories throughout the day
•Eat food like Nuts, Dried Fruits, Grains, Meat, Potatoes, dark chocolate, peanut butter, etc •You can avoid eating tons of vegetables if gaining weight is a priority
•It's very important to lift heavy weights and improve your strength •This will help you gain muscle mass instead of just fat •Try to lift weight at least 3 times a week