I would have to see a picture but I like to see a dog thinner than fatter!
A lot of people feel the need to fatten up their dog when they don't really need it.
I like Jackson on the thinner side. In the winter, he was 16lbs, and now he's 15.1lbs approx. and at a perfect weight for his frame. See how you can see the little tuck where his waist is?