Are those the little fat ticks in your avatar ?
that made me laugh but in all honesty - It does sound like a puppy diet is in order... I'd love to see photos of the little chubbos....
I know people think chubby puppies are so cute but hopefully you can get that weight under control - not using their legs can't be good...I've not heard of that. Is the vet sure it's due to the extra weight ? (I hope so !)
all the best !