What Can I Do To Help My Dog Gain Weight?

Is he neutered? He will naturally stay thin with the active hormones in his body until the testicles are removed but you then have to be careful that he doesn't gain too much weight after that. You can also try a higher protein diet and make sure that it's one of the highest quality foods you can buy...i.e. Iams or Science Diet and even Eukanuba.

Be very careful what foods you give your pup.  Here is a list of poisonous and toxic foods:

 
Call your vet for more clarification and make an appointment for your doggie!

One of our dogs stopped eating so we would put hot water on the food and the dog would let it soften the food a bit before it ate it.  We had figured that it was harder for him to eat being such a small dog.

Quit feeding him people food, there are foods that are formulated to suit what the dogs needs, and definitely do not feed the pup any more butter! It will not only act as a laxative, it is bad for people, and it's bad for animals. Exercise the pup, and that should naturally bring up the pups hunger. If it does get worse, I strongly suggest that you take it to the vet. Hope this helps, good luck.

You're covering his food in butter?! Could be why he isn't eating!  2.1 lb for a teacup poodle is a good weight.  They usually weigh between 2-4 lbs when fully grown, with 3 lbs being the average weight. Maybe he just doesn't like dry food; try mixing 1/2 dry with 1/2 wet. If he still isn't eating that, change to wet altogether. Watch what he eats in the fruits and veggie dept., grapes are harmful. Check w/your vet as far as that goes to know exactly which ones are harmful and which ones he can have.  If your dog won't eat what I suggested, then something else is wrong and you will need to see a vet. Good luck!