BCAA's have a tiny insulin response compared to carbs. They taste like shit so you will need to combine them with a diet (no sugar no calories flavored drink). If your goal is to lose fat only (and not muscle) then you have to take BCAA's as they will spare muscle loss while maintaining most of the fasted state fat loss effects. If you want to lose maximum fat and don't mind losing muscle as well then don't take the BCAA's before doing fasted cardio. Yohimbine is particularily effective when used in a fasted state. I take BCAA's, Yohimbine/Yohimflame whatever, before fasted cardio in the morning and the fat melts off 1-2 pound a week even at low digits. Combine with Caffeine, aspirin, synephrine, and Amp-C for even more fat burning synergy.