i also read, that bcaas would help in fatloss, because the body recognizes amino acids in the blood stream and thinks he would burn muscles, so he burns more fat than muscles. but i dont know where i read it, could have been a supplement site, so it could be marketing.

Out of curiosity, where are you finding the "mixed" reviews?

They prevent muscle breakdown. In my case yes they do work. Say im 217 pounds before bed. I wake up 210. If I use BCAA's I wake up heavier than 210 maybe by a pound or so. Certain medical conditions utilize BCAA's to help prevent muscle breakdown. If doctors prescribe it imo its gotta be good. If your getting these BCAAs already in your diet and from your body you may not find them particularly usefull.