Sometimes people wear the same clothes for days no matter how sweaty those clothes get. The best way to deal with this situation is talk to this member in private and let him know that others have complained (if you are the manager you should do it or let your manager know about it). Some people have poor sense of smell and/or after sometime of smelling the same odor their nose becomes desensitized to it. Tough spot to be, but the bottom line is that one person cannot make it harder for others to be there.
body odor can actually be the result of a metabolic disorder of which the customer is not aware. This may be the best angle to approach this sensitive subject. Here is a link to an article talking about it http://www.medicinenet.com/script/main/art.asp?articlekey=149212. It is quite possible that the customer is not aware of it because few people have the courage to address it because it is awkward.
Credit to you for wanting to find a diplomatic way.