Yeah, 600 cal/hr is z1 for me, but I didn’t want to be presumptuous about Shisheveudysgj. 
Higher wattages do give some headroom for increased weight loss, particularly since it should be more fat (than carbs) burned in zone 1 and 2. Also means the carb fuel burns it faster in the higher zones. Unfortunately, I’ve been fueling like a TDR participant, while riding like a 2nd year cyclist for the last half-dozen years, so for me, my burn rate has finally caught up to my diet, lol.