Momo was 4 lbs before & 5 now...can't feel his rib cage anymore...he's a rollie pollie, bouncin around like a ball!

He's always had a good appetite, now he doesn't eat as much, but has gained a whole lb & yes, a lb is alot for a tiny yorkie. He does this really cute 'hi' thing w/his paws & I can't not give him treats! I guess it's mommie's fault...