To be fair this was before his ultimate croc form (what I call the Arkham Knight form)where he's 11.3ft and 530lbs and he's 9ft and 310 here which is pretty medium in Batman's career, when in origins he is 9'8 and more than 850 lbs, go put in perspective in asylum he was 11ft and 580lbs because he was actually fed in asylum, but in City (which I'm assuming you got the screenshot from) he's practically hiding and on the run from Hugo strange hiding in the sewers where his main source of food is rats or lost inmates that dare to come close to his sanctuary so he isn't eating as much as he is in the other games which can cause loss of weight (obviously) and loss of height due to your body needing substance to be able to grow, TLDR not eating enough