Fon is fat and nobody believes me

Fon weighed 6.4 kg at the vet last month. The vet said his ideal weight is around 4.5, so we have a problem. Kao and Miso think this is hilarious, they both stare at him when he waddles to the bowl. I have to admit we spoil him. He sits on the kitchen counter when we cook, so we give him little pieces of chicken, and then my girlfriend gives him treats when she watches series. I did not realise how much this adds up until the vet made me write down everything in a notebook for one week. Now the plan is simple. Wet food in the morning, dry food in the evening measured by the cup, not by hand. No treats except one small one on Sunday. The dogs have to stop sharing their food with him too, which Miso does not understand at all. Miso is a Siberian Husky, he eats anything, he eats the cat's food also. Fon is not happy. He sits in front of the fridge and makes a sound like he is dying. We are at day 9 now. I lost one kilo myself from walking him around the soi, so maybe it is working for both of us. The condo juristic office has a small garden with a path, I take him there in the evening. He walks 5 minutes and then he wants to go back home. I think he thinks we are crazy. I will update in 1 month with the weight. Maybe he is at 5.9 now, the vet said do not panic.