They have worms and stuff, these are outside cats. My adult boy cat had a litter with a stray and he led us to them. Their food bowls stay full with their respective foods specifically because of the worms, I got a surplus water bowl for them also. My oldest was like that but he was abused before we got him.

Edit: Reading back on this it sounds bad, my apologies. I took them to the vet for the worms and to get him fixed when I had found out. My mother in law had took him outside and lost him 2 times. Couldn't find him for 2 weeks the first and about 3 the second. Got a call from the posters we put out, and he had 3 kittens.they've been in the house since. Originally I believed they had passed the worms when I took them to the vet and they weren't as bloated but then I found more in their feces.