To increase weight eat food more frequently with extra amount.Do not skip meals.Take cake,pastries,dark chocolate,ghee,cream,cheese,butter.Eat fish,egg,skimmed milk,soy milk,soybean,soy product,tofu,mushroom.Take seeds,nuts.Use healthy fat in cooking extra.Drink lots of water but not
just before or during meals.Avoid fast foods as
far as possible.Avoid smoking,alcohol.Do muscle building exercise to gain weight as well as to be muscular.