How To Put Weight On A Kitten?

Question: My cat is 6 years old and has gained weight. She used to be thin, but now she’s fat. I don’t know how much weight she’s lost or gained, but she looks a lot different than before.

My vet suggested putting her on a low-fat diet, so I did that for a while and even took her off dry food completely. But she doesn’t seem to have gotten any thinner at all…she’s still overweight! We tried switching brands of wet food, too – no luck there either! What can we do? It’s really frustrating because my kitten is healthy otherwise—she eats well and has been checked by the vet more times than I would like (and more often than my other cats). How long does it take for this problem to get better? Should we try something else instead of putting her back on dry food again? Thanks in advance for your help–I hate seeing my little kitty sad 🙁