We took care of my sister-in-law's Yorkie (I HATE yappie dogs) for 8 months while it was getting cancer treatment (don't ask). When we got it, it weighted 18 lbs...no kidding. It could not walk off pavement because its gut dragged so low. It wheezed constantly because it was so fat it could hardly breath.

I told my wife if the dog was going to live with us it was going to live by my rules. So I asked the vet the minimum diet and that was ALL it got. Since I hated it it was easy to ignore its begging. We got an elevated dog bowl stand for my spaniel so that the runt could not reach his food.

Within 6 months the little jerk was down to ideal weight (8 lbs I think), could tear around the yard at a dead run, and was enjoying life. His weight became self-regulating when he got light enough to chin-up into the spaniel's bowl and eat...then he'd gain another ounce and not be able to reach anymore. Problem solved.

Finally he went back to his owner and within a year was back up to 16 lbs. It's all what you feed them.