Turtles are known to get obessed in captivity, because there are big gluttons. They tend to over eat, due on the part of there caretakers not knowing this. In the wild they have to work for food so the pounds stay off and they dont get a guarenteed meal everday. I have three turtles and boy does my female pennslyvania cooter love to eat all day if I would let her. It's funny she actually knows when it's feeding time and will look up at me and beg for more food, sounds weird, but you would have to see it, it's quite funny. When I grab her food container and shake it she will slide really fast off her basking dock into the water and swim up and down the sides of her tank and will look at the food container and let the food rain on her face. Also anytime I get into her tank stand she thinks it's feeding time day or night if I open up the stand which is where her food is located she starts splashing about looking up at me. They dont grow superfast but my turtle being a female and a totally different species, when I got her she was 4 inches and 4 years and 6 months later she is now at 13 inches in circumfrence.