When we are out walking, Teddy will sometimes sniff near Max's belly (both are neutered). They both like to mark outdoors and I think Teddy is "checking in". I clap my hands and call Teddy's name, and he stops.
I would try that with Lui every time he does it. Maybe even add in "no!". Keep trying to redirect his attention.
By the way, being unneutered will also contribute to thinness. Breeders often have to increase their stud's food intake when a girl in heat is around.
__________________ Kristin, Max and Teddy  |