You can tell by the pads on the head, cheeks, legs and tail. The fat pads on the head and the cheeks should not be indented but they should not be bulging out to extremes. The tail and legs should also be nice and plump but not over plump. I know, not the best description I would post pictures or threads of chams that are underweight, over weight and in the middle but I do not want to single anyone out. Especially the ones I have mentioned to that their cham is over weight and they didnt want to hear it Ill try to find some threads and PM you the links of some of these animals so you can get a good comparison.