My cat has been overweight ever since. He had to lose weigth for a surgery, so I put him on a diet in 2017. He got less of his regular wet food mixed with water and "food cellulose", some kind of Slim Fast for animals with 0 calories and 0 anything - just dietary fiber. His weight went down from 8.5 kg to 7 kg in a few months and he's been visibly thinner than before. He kept his lower weight for more than a year, and we kept mixing his food with food cellulose and water.
A few months ago, he started gaining weight again, although he gets less than the suggested daily ration, still mixed with cellulose, plus we cut the dry food to a total minimum because it's unhealthy and we didn't want him to become fatter. But still, he's back to 8.3 kg. This happened through the last 3-4 months and we can't explain it.
According to the food can, a 5 kg cat's daily ration is 245g,so the ration for a 7 kg cat would be about 350g of food daily. We give the cat 260g for 7kg plus the cellulose, and yet he gained 1.3 kg of weight in the last few months.
I asked in an online forum and they told me to dismiss the cellulose and feed the cat more wet food, calculated to his actual weight, because he's gaining weight from lack of proteins, or that his metabolism is messed up because of the diet. Can someone approve this or has another idea?
Additional information: the cat is 8 years old, neutered and healthy. He's an outside cat and goes for long walks, catches mice and seems fit and normal, but inside the house, he doesn't move much.