You could try dividing their food up into different eating areas/kitchens and placing them in different locations.
But are you sure he is overweight? I think some gliders just like to eat more than others, or some like "more" types of food...they aren't so picky.
Jasper(M), Kodah(M),Zoey(F) are all the same age. I weighed them on the 2nd... Jazz is 101g. Kod is 164g. & Zoe is 102g.
Kodah loves his food, but he also runs on the Stealth pretty often but he's the heaviest of them all.
Jazz doesn't over eat & he never gets on the wheel.
Zoe doesn't over eat & she runs on the wheel about as much as Kodah does.
I do spread food throughout their environment simply for foraging opportunities and I've never seen any food aggression...Actually Kodah will go into the kitchen, get him a nibble of something and exit to eat it elsewhere so they all have the opportunity to get food. I think just like humans, some just hold onto the weight where others burn it off quickly.
But try spreading the food out and see if that helps.