Exercise physiologists used to believe that “steady state” cardio was superior for fat loss because relatively more fat is used by the body as fuel at lower exercise intensities than at higher intensities. The Fat Burning Zone shown on most cardio equipment as only 60%-65% of max heart rate is really a myth and is NOT optimal for burning fat. Yes, you burn more fat relative to glycogen when going for a walk, but what we care about is total fat burn. At higher intensities, you are burning far more fat, even though the fat/glycogen ratio is lower. In addition, interval training allows you to exercise at very high intensities for a much longer period of time than steady state, so you burn more fat.
As an added bonus, there’s also an afterburn effect known as EPOC (excess-post exercise oxygen consumption). You increase your metabolism
and burn more calories for up to 24 hours after interval training, whereas going for a jog burns almost NO calories after.