I'm a noob just starting out to jogging, I've just been doing bjj for awhile. I've read that 60%-70% HR zone was great for fat loss, I'm in my 20's and that turns out to be 120-140bpm. My concern was that after a 45min jog I've done 3mi and I love that fact that I'm not trying to push myself but it just seems too good to be true. It seems too easy. The next level is 70%-80% 140-160bpm and wouldn't this rate allow me to lose fat faster? I'd obviously be losing more calories in a 45min jog than at 60-70 but just wanted some confirmation that the calories won't be at the cost of muscle mass. Should I up the HR or up the durations of the lower HR zone? Thanks!