Like China mentioned being low bf causes fatigue. Add on top of that low calories, fasted morning cardio and simulants your energy is gone. For me, clen adds a wired feeling on top of being tired, a very unpleaseing feeling for the difference of a negigable amount of bf. Just not worth it unless you are competing. I dieted for 6 months last year, just wasted to be the lean guy with all the events I had, got submerged at 5.5%.. Was an awesome summer, had a lot of fun but was dizzy onto of being tired. You need to be aware of the sacrifice, you will feel crummy, I don't know how pros do it, they are warriors