[Maximo]

I have read in other forums that thinness can be a challenge on raw, especially with the prey model raw.

We know a pug who eats raw. At first we were really impressed how great he looked because most other pugs we know are overweight. Now he looks scary thin.

Runny poop can be caused by so many things, but is not normal on a raw diet. If he has problems while staying with you, that might be a good place to start with your friend. If Lui's ribcage is really prominent, I would just point it out to your friend in a matter of fact way. Suggest a vet check the runny poop, and the vet will automatically assess the dog's weight.