The most important thing you can do to gain weight is to create a calorie surplus meaning you eat more calories than your body needs. You can determine your calorie needs using this Calorie Calculator. If you want to gain weight slowly and steadily, aim for 300 to 500 calories more than you burn each day according to the calculator. If you want to gain fast, aim for around 700 to 1000 calories above your maintenance level. Keeping in mind that Calorie Calculator only provide estimate. Your needs may vary by several hundred calories per day, give or take. Eat plenty of Protein: The single most important nutrient for gaining weight is protein for muscle is made of protein and without it most of those extra calories may end up as body fat. Studies show that during periods of overfeeding, high protein diet causes many of the extra calories to be turned into muscle. However, keeping in mind that protein is a double edged sword. It is also highly filling, which may...