rule number one is dont but from GNC, they are the most overpriced supplement store ive seen. Use bodybuilding.com. As for weight gainers, they are not healthy and cost a lot per serving. They are usually filled with sugars or a sugar like substance called maltodextrin which is a little trick companies use. maltodextrin is like a sugar but isnt so they dont count it in the nutrition label section for sugar. Making your own gainer is healthier and cheaper. You can easily get anywhere from 600-1000+ calories in a shake consisting of regular house hold items and protein. Examples: whey protein, peanut butter, oats, bananas, and of course milk among many others.