Cannot put on fat either. Lifting is actually the only way I found to gain any weight and that was purely from muscle. I have to eat a ton and workout. I also have to keep it up because if I take off 2-3 weeks all the gain I made gradually drops until I'm back at square one. I won't gain a thing sitting back and eating, it burns right out of me. People that think you hardly ever eat have no idea. The only way I think I could gain 20-25 lbs would be through steroids.