I have 4 Chihuahuas. I've had the 2 older dogs for 11 and 12 years. The boy has always been tiny, about 4 lbs, and the girl has always been bigger, about 15 lbs, but not overweight or obese. She is very proportionate.
About 2 1/2 years ago she had puppies and we would up keeping 2 of them. Well, we kept one, a girl and give one to my daughter and she had him for about a year and we have him now for about 1 1/2 years. Up until July, 2010 they were both normal sized. The girl was tiny, about 5 lbs and the boy was bigger, around 8 lbs. After I had my surgery that changed, mainly because we have a lot more leftovers now and I hate to throw things out so they get them. I have always given them people food with no problems but it was a much smaller quantity. Now, because my daughter and I don't eat the same any more there are always more leftovers because I'm not eating things like macaroni and cheese or hamburger helper so it goes to the dogs. And I also give them the rest of my meals that I can't finish, plus anything we bring back from a restaurant that isn't eaten. Plus their regular food. They have turned into little pigs, always begging for food.
Now the little girl weighs about 12 lbs and the boy about 16 lbs. Even their mother has put on a few pounds. Only my oldest dog, JJ, has stayed small. I know I'm not doing them any favors but it is so hard to say no to them and I hate wasting food.
Here is Princess
This is Pepper