Chiuhauha owners Question?

I have a 22 month old chiuhauha and he is so skinny. I am concerned because he eats well and never really gains weight. I dont want a fat dog but his weight just doesnt look right. any ideas?

Thanks in advance

I don't own a chiuhauha, but this happened to a few of my customers, and the result was an overactive thyroid-I would have him checked out just to be on the safe side.

Also, if he's a very active dog, he could be eating up his calories with energy-If this is the case I would switch him back to puppy food, or a high energy brand-they have more fat and protein in them.