Feeding a no-grain dry food would be no different to feeding a good quality grain-free wet food except that the wet food would be better for your cat due to the moisture content. Your cat can be slim on wet food and is more likely to be as wet fills up quicker and reduces the need for the cat to keep eating like they sometimes do with dry.

Also, as already said, BSH's are chunky wee monkeys and so 4kg is not overweight at all. My Abby was 3.5kg at 10mths and she is NOT a BSH!!!

Finally, a hanging tummy is NOT always a sign of overweight. You need to look at your cat closely if they have this because some cats have a sort of extra skin (it has a proper name which I can't remember) which hangs down and can give the appearance of being a flabby belly but it actually isin't.

Hope that helps you a bit.

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Thank you very much, very reassuring to know.