Managed to lose around nearly a stone in 6 weeks when our dog was a puppy and needed lots of walking.
Nearly 8 years later she does not need nearly as much walking and more or less tells us when she has had enough, so sadly the pounds have gradually went back on.
I try and do at least 10.000 steps on my days off, though I suppose alot of it is sticking to a good diet which ain't easy just now.