Personally I feel that vets comment on weight and maturity of cats as "normal" moggies, it doesn't matter whether you take in a normal moggy or a pedigree... like yours a Persian, a Ragdoll etc etc. They normally always say "oh they're overweight" because they're using normal moggy sizes and weights. We all know that some pedigree cats are large and that's how they are supposed to be.

Take Ragdolls for example, they are the 2nd largest breed of cat. I took one of my Ragdolls Bailey in for a check up once... she weighed him and he weighed about 10lbs and she said he was overweight and needed to lose weight. Ragdolls (males) can weight upto 22lbs... so, I know he wasn't overweight like the vet was saying... he now weighs 18lbs.

I feel that vets put every dog or cat down to the statistics of a normal mongrel dog or moggy cat when infact they should be going on specific breed stastistics!!! in my opinion.

I am not an expert on Persians... there are some Persian breeders on this site, so maybe they will be able to help more than I can. From what I have read, Persians can weigh anything between 7-12 lbs?? ... You say your cat weighs around 4.5kg's well thats around 9.5lbs roughly and your vet is saying he should weigh 6lbs.