Thanks for your reply. could you please brief me about my diet which will help me to gain weight iinstantly?

Weight gain diet: First eat healthy. At least 5 servings of fruits and vegetables a day. Lots of grains, nuts, cereals. You are in the fortunate situation where you can eat a lot of foods that most have to avoid like ice cream and milk shakes (very high sources of calories and fat). Starches too are fine for you: potatoes and pasta. Eat at least 4 ounces of meat or fish daily.

There are no...: ....Healthy diets that will make you gain weight instantly. It is also unlikely, unless you are malnourished, that you need to gain weight. If you eat a healthy diet and you are thin, then your body is the weight it should be.