Even more so than gender, Breed is the most important factor in assessing your cat's ideal weight.
CAT BODY SHAPE GUIDE: FAT OR NOT?
Step 1: Move your hands along the side of your cat's body and to feel the ribs.
Step 2: If your cat is within ideal weight you will have no problem counting the number of ribs (there will be fat around the ribs, that is normal, but you should be able to feel them easily)
I have had Lois & Clark, my two, 7-month-old kittens, for 3 months. Lois is a girl and Clark is her brother. Lois has a potbelly. Should she be fat? Will she grow into it? They also have a gas problem. They are both active and have no signs of sickness. - Tony
No, Lois should not be overweight. Bad eating habits and odd feeding times can have a negative effect on your kitties' health. Be sure that you follow a routine feeding schedule and that you not leave a buffet-style meal out for Lois & Clark.
Feed your tikes kitten/cat food only and restrict the feedings to the recommended quantities. Fresh water should be made available to them all day. In case your cats eat human food, please stop them from doing so. While cats love human food, it is not good for them and can lead to weight gain and all sorts of other problems. Click here for a body shape guide. Simba
My sister and I recently got two, 6-week-old kittens. They seemed to like us and their new home, but my kitten got fatter while my sister's seemed skinny. Also, My sister's kitten started licking my kitten's paw making a slurping sound. What does it mean? And how much should 10 to 12-week-old kittens weigh and/or on what should we weigh them on. Thanks, Carla
do not worry about the slurping, the kitten is exhibiting a behavior from her nursing days and it is all harmless (read more in Newborn Kitten Care).
The weight difference is a trickier situation. There are a couple of potential causes. It is possible that the your sister's kitten just has a larger frame than the other. Another cause could be that one kitten may be eating more and/or exercising less than the other. If they are fed together, observe what quantities each of them eat. Also, be sure that both you and your sister are carefully following your kitten food's directions.
Another cause may be general health. If you have not done so already, take the kittens to the vet for their shots (they are at the right age). Have your vet test each kitten for the normal ailments since it is always possible that the little kitten may have an illness. As for their ideal weight, it will vary by breed. Your vet should be able to tell you how the little guys are doing relative to where they should be. Simba