I see no reason why it wouldn't be suitable for athletes. It's not like you feel tired and run down all day. I've been on it for 13 weeks now and feel GREAT...not too mention the complete transformation I did to my physique.
SGX is all about timing your macro nutrients so you able to burn and incredible amount of fat while still adding LBM.....naturaly too. The first 8 weeks on the program I added 50lbs to my dead lifts and squats, and about 30lbs to my incline presses...I was natural then and also dropped 20lbs of body weight. I've since started "supplementing" and my weight has stayed the same, but my BF level is dropping every week.