From what I've read and heard, HCG increases fat loss, making it a useful adjunct to diet and exercise programs. I've known many women who've done the injections with good results, and none have described any side-effects at all.
The dosage may be higher for fertility purposes, perhaps?
http://www.hcgobesity.org/hcg_obesity_opinions.htm
http://hcgobesity.org/hcg1.htm
There is lots of info on the net about hcg-- some positive, but mostly negative it seems.