Some thoughts on a constantly hungry kitten.
I was reading through all the comments and noticed that feeding free choice was not usually considered for this kitten. Kittens need lots of calories for growth and to support their high activity level. In my experience feeding free choice is almost never a problem, as long as protein and fat are fed at high levels and in balance. Balance in a wet food would be 12% protein and 6% fat. This canned food would have very little starch in it so you could feed a kitten a canned food with less protein and fat since most kittens do well with about 10% starch in their diet. I have found that about 2 parts protein to 1 part fat is a good rule of thumb.
I just wanted to include some of my thoughts on free feeding of all cats. It is not natural for cats to overeat in the wild. If they did so in the wild, they would collapse their food chain and eventually starve or have to move to a new territory. New territories already contain predators so they would have to fight each other to stay there; winner take all. They would also become obese and become less successful at hunting and avoiding predators. So to my mind I think it unlikely that they would be programed to overeat. I would also like to mention that cats in the wild consume the same level of protein and fat their whole lives. Kittens and adults thrive on the same diet in the wild and I believe they will only eat to meet their energy demands when fed that way in our homes.
It is my personal belief through observation and experience that overeating and the resulting weight gain usually only occurs with the feeding of a substandard diet. Keep in mind that a diet that may work for one cat, may not work for another. All cats are carnivores and are meant to thrive on diets consisting primarily of protein and fat. I believe that starch is the reason our cats deviate from their natural instincts. I have found that once you remove excess starch from their diet, they return to a normal eating pattern and do not overeat or become overweight.
My recommendation for this cat would be to feed wet food of high protein and fat as mentioned above, 3 times a day. First thing in the morning, again at 4:00 – 5:00pm and the third time just before bed. I would also recommend that you procure the highest protein and fat kibble you can find and have a dish available at all times. As long as the kibble has roughly 2 parts protein to 1 part fat and the carbs are less than 10% you should have great results and a very satisfied kitty.
Please let everyone know what ends up working for your kitten.