straight whey with no carbs and no fats...up to 70% can be oxidized.
why are you using straight whey ? is it post workout ? if not you should be using a blended protein. and if so why no carbs post workout, it will not effect fat loss (it may stop lipolysis for a short period but no big deal). post workout is the safest time to ingest carbs w/o fear of fat storage.
the only supp. that has been proved to slow the modulation of whey is Fibersol or Fibersol II...