I didn't start noticing any extra fat loss until I actually started doing cardio whiel on GW. I'm not talking 10-15min of HIT 2-3 times a week. I'm talking almost daily steady state 30min and up.
Even if GW doesn't actually burn any extra fat on it's own, the pace I can keep up now for steady state is burning much more calories than I could ever before. Plus cardio feels so much easier now that it's a joy to do, I'm constantly impressing myself now when it comes to cardio.
And before GW I fucking hated cardio.