In order to build muscle mass you need to be consuming more calories that you burn, every day. If you need an easy way to get a good serving of quality whey protein, complex carbs and fats, then weight gainers are for you! Weight gainers are very versatile! You can use them at any time of the day, for your post workout shake, and for meal replacements. If you're looking to gain weight and muscle mass fast, then a good quality weight gainer is just what you need.