Every morning when I go to feed the dogs (or afternoon, if I forgot to thaw out their breakfast the night before!), Koira looks exceptionally skinny. Her spine appears to stick out, her ribs are super obvious, with sunken spaces between them, and her waist is teeny tiny. She almost had me convinced she needed to gain some weight. I even increased her food a bit for a while. It didn't seem to make any difference.
Then, I noticed something. Koira doesn't look exceptionally skinny any other times. She is in shape, her ribs certainly show a bit, and a tiny curve of spine, but that is a healthy look on a dog with her build.
I think Koira is sucking in her belly at meal times. I think she has realized it makes her look starving and pathetic, and is milking it for all its worth. Silly beast.