When you're Torrenting your ISP can see that you're using it's service for Torrenting and may decide to throttle your internet connection and slow it down.
However most ISPS do not care what you're downloading anymore but if they really wanted to they could slow down your connection or even terminate your service if it's in the contract and terms and conditions.
On FIOS internet or DSL you're unlikely to get throttled back or terminated but on a cable internet connection or Satellite internet connection they might throttle you back for Torrenting.