Pics above.
Kitty is around 10 years old, spayed female. The little green mark that can be seen in the above images are remnants of her spay stitches.
I'm not sure why her belly has less fur, it's been this way ever since I returned to the US from an extended stay abroad around two months ago (she lives with family). Wasn't like this from what I remember when I left the US in April of last year (returned November).
She hasn't been liking the food family bought her so I purchased a different brand a few days ago that I know she likes more, which she has been enjoying. From a look when taking these pics today it does seem like there is a bit more fur on the belly than before, so perhaps the change in diet helped. Otherwise, she eats, drinks, and uses her litterbox normally.
Does anyone else have a cat with this? At first I thought it was because she was quite old and the age was just showing; her tail thinned out considerably in the last year, she is no longer as eager to jump high distances, and does not go as crazy playing with the laser pointer...but still does! lol. But there do seem to be improvements in the belly area and she's acting perfectly fine.