Well, there is good news and bad news. In most cases, weight gain is caused by simply overeating. With cats especially, since they are very small, even a tiny amount of weight gain can be very noticeable. We are learning more and more that obesity is a very serious condition for our pets. The best offense, in this case, is a good defense. Weigh your pet often and be mindful of any weight gain.
Now, is there a possibility that there are underlying diseases that can cause weight gain? Absolutely. Cushing’s disease is a prime example of this but it causes weight gain by causing the animal to have the need to eat pretty much non-stop. The one thing that can sometimes trick you is if a pet develops fluids in its belly. This can be a rapid expansion of the abdomen that can look like weight gain but it really isn’t and it will come on quickly. The belly tends to look bloated and feel tight and we recommend getting this checked out as soon as possible.
To summarize, weight gain is something that typically happens over a long period of time, but it often appears to suddenly come on all at once. Keep your pets fit, they will thank you for it!