I don't know what's actually in it, I can only tell you my personal experience. I used to take only protein. Then I wanted to put on some bulk so I bought a 10lb tub of N-large. I will just say that it definitely worked for me. You will very likely put on some weight by taking this stuff. However for me it put some fat around the midsection....which is likely going to happen with any weight gainer unless you are like 17 years old and have the metabolism of a humming bird. I stopped taking it after about 7-8 pounds of it b/c I was simply gaining more fat than I wanted. You could probably make a better weight gaininer from oats, flax/fish, whey and milk (less sugar than many weight gainers) but for ease of use and gaining weight in general it does work.