I actually do more energy expenditure through cardio rather than cut calories. Granted, this amounts to slow fat loss but it does ensure less muscle wasting, too. I'm think a combination of both cutting calories and increasing expenditures through cardio is the best bet for most people though as cutting fat by calorie deficit alone will come at the expense of your muscle mass.
Now, is LISS a subjective thing? Or is there a quantifiable measurement to decide what is LISS and what is HIIT/HIT?
I like 70-80% of MAX heart rate for 15-20 minutes. Granted, I could easily maintain such a workout for 40 minutes or longer if I wanted to. Does that make it LISS or is it still considered High Intensity? My understanding is that your heart rate ultimately determines the type of aerobics that you are doing.
The explanation for LISS hurting muscle gain is an easy explanation: it pulls so many calories at a time, robbing your muscles of glycogen & amino acids in the process. Being deprived of both, and likely not being able to eat a caloric surplus (as is the case for many endurance runners) equates to small muscle mass. You pull from your muscles so much in long endurance training that its hard to give the muscle enough nutrients to actually grow. This has been observed in studies as early as the 70's and 80's.