My little dog is turning into a blimp

There was a time when I looked desperately for an appetite suppressant for my little blimp of a dog. I did find a great dog food for senior dogs (he is 7 or 8 years old) that worked well, but the store I got it at no longer carries it. I switched him back to a regular dog food and then found out he was begging food from our neighbor who thinks he is cute.

So now he is restricted from making visits to the neighbors but then he was stealing food from our cats. So what to do? After almost pulling my hair out over a growing blimp with 4 legs, he stopped gaining weight and is starting to be very fit. I am at a loss to what is going on with his body. The only thing I can think of is that he no longer likes the taste of the cat food and has stopped eating it.

Now I wonder how long it will be before he starts to gain weight again. He seems to be what us horse owners call an "easy keeper".