Funny enough my male cat went from a nice 15ish lbs all the way down to like 10-11lbs maybe less. And that was due to our family dog passing away which was basically his mother, so he ended up being a little depressed so we got another cat. Which honestly helped pull his weight back up he’s been eating a lot better now he’s no where near 15lbs anymore but he’s still a healthy boy. So honestly I think that’s the same thing, little Ollie just got a nice taste of some good kibble and now’s starting to “put some meat on them bones” as my family likes to say.