Do your ISP a favor and use a VPN when torrenting. They will know you're torrenting based on traffic patterns, but they won't know what you're torrenting. That way they don't have to serve you a notice or kick you off their service at the behest of movie or music studios. Your ISP may not care what you're doing, but those businesses do, and the law is on their side.
VPN makes it extremely difficult for your ISP to spy on you, which is the whole point.
The nature of uploads/downloads happening with torrents coming and going from disparate sources. Apparently it has a certain network signature that can be identified fairly reliably. ISPs don't really give a shit about WHAT you torrent, but they will try to traffic shape it so it doesn't affect other users on the ISP much.