Molly went from 14lbs to 16lbs after she was spayed. i have been cutting down her food a bit and she is now back to her ideal weight of 14lbs. I havent noticed any spare bits on her tummy though, but she does get lots of exercise every day. She chases a ball round the fields for 20mins non stop each day and then has an hours walk on top of that.
I would get your pup checked at the vets if you are really worried.
