I knew a kid in college (pre-med!) that could take 3 amps of Sust a week and he would just BLOW UP. He'd go on for 8 weeks or so, then come off for about the same amount of time, and not lose but @ 10 lbs or so. He had a rule of time off=time on.
He also smoked weed before he trained to dull the pain and after he trained to stimulate appetite. I've never seen a human being (pound for pound) eat that much!
Just goes to show, genetically, there sre just some that are a step ahead...