Hi there,
Weirdly, I have found the same at times, usually when I'm starting to get things under control a little though.
I've been told by my doctors that its my body's way of telling me it needs more. When we flare, it takes a lot of energy to repair the damage so sometimes we need extra calories to fuel the fire so to speak. It can also be the way your body tries to rebuild fat and nutrient stores that can be used up when you're sick.
It might also be that you have some nutrient deficiencies developing, so your body triggers an 'eat more' response to compensate. When you're better, you maybe dont need as much energy and the deficiencies have corrected themselves, so you dont feel the need to eat as much.
I hope this makes sense.