Jen I wouldn't worry about it unless she loses more. I don't know if I'm the only one but I think you need to get a second opinion. I think it's ridiculous that your vet would tell you Tee Tee needs to lose a pound

Yorkies generally have a standard frame and actually 3 lbs is below the standard so I'm not really sure why he would tell you 4 lbs is overweight for her?

You've seen Coco and she has a tiny frame and tiny bones but she's a healthy almost 5 lbs. I would keep doing what you've been doing and consider a second opinion because I think it's crazy that he would tell you to put her on a diet

I think you should feed her normal stuff and don't worry too much. If she continues to lose weight then get a blood test but otherwise I'm sure she's fine. Just fatten her up a little please, I think your vet needs to be hit upside the head. Poor Tee Tee