Overweight four year old

[Nicketynac]

My DS will be five in December. At the start of the summer we realised he had put on weight as he was too big for his 4-5year old clothes. Up until then he had seemed healthy weight and height although we hadn't actually weighed him, but had always fitted into age appropriate clothes. I think some of his weight gain was related to DD being born in March and me being less active with him as a result, plus maybe some anxiety about starting school.
Anyway, we checked his weight/ height and his BMI was above 20, which is obese for his age. We talked to him about healthy eating choices, changed sweets and pudding to a more occasional treat and eventually got the grandparents on board. (They were terrible with treats and portion sizes.) We eat more home-made meals as a family. We have enrolled him in a few extracurricular activities, bought him a trampoline and spent more time playing outside with him.
Anyway, I weighed him today and he has lost 600g since July. He has not got any taller (which I think is a good thing as I have read that kids who eat too much often get taller than usual due to hormones, could be wrong).
NHS choices website encourages weight loss for over fives but weight maintenance for under fives, and let them grow into their weight if you see what I mean.
I am just a bit worried as I am not sure what else we can do. I don't want to ban treats altogether and I certainly don't want him being conscious of his weight.
We have spoken mainly about health, fitness, strong muscles and teeth. He seems as fit as other kids in his class when I see them playing together but he definitely has the biggest tummy. DH is overweight but is a rugby player so claims some of it is muscle . He was healthy weight as a child.
Any ideas? Should I keep going the way we are or aim for more weight loss?

Can you give some idea of his average daily menus? It's hard to see sometimes when it's your own child, what's normal and what's not normal.

Avoid talking to him about it. At that age his diet is your responsibility not his.
But it sounds as if it's going in the right direction.

Breakfast: small bowl of Shreddies, Rice Krispies or one Weetabix
Snack at school: small no-added sugar carrot muffin (recipe from baby-led weaning cookbook), handful of grapes or blueberries. He eats variable amount at playtime, ranging from everything to nothing.
Lunch: usually a sandwich or soup and half a sandwich. At school he usually chooses the cold lunch which is sandwich and yoghurt (plus fruit which he may or may not eat) or a picking plate which seems to be cheese, cold meat, oat cake, cucumber, carrot sticks etc. There is no choice on the picking plate I.e. If he doesn't want cucumber he doesn't get extra cheese. Dinner: Usually home-made, chicken curry, fajitas etc. Once a week we have frozen pizza which he gets a quarter, plus veg (he "hates veg" except sweetcorn and peas, everything else has to be hidden in sauce or mash.) We have cut down on portion sizes but that sometimes means he asks for a snack ten minutes after dinner!
Snacks at home are a challenge. He never wants fruit, might take it once he realises he isn't getting anything else, but asks for another snack straight away after eating so I think a lot of it is habit.
I am happy that he hasn't put on any more weight but just not sure if we should be aiming for maintenance or loss. He needs to lose about 3kg to be in the healthy BMI range, maybe 1kg to get in the overweight range.

That doesn't sound like a bad diet at all OP...I can only suggest he needs more exercise..I stopped buying ANY snacks apart from fruit when one of my DD's began looking a bit chubby....she knows now that it's fruit, carrots or nothing. I do get something for Fridays though...crisps or chocolate. I make muffins once a week and they last 2 days. DD is now a good weight. .

Have you used the NHS online bmi calculator and selected child? Just wondering as when I put my dd's details it just gives a centile and says whether healthy or not. If I add 4kg to her actual weight it just says very overweight and 99th centile, so not sure where you have got the 20 from and whether it is accurate? Best to use the NHS calculator so you know the figures are correct!

I just tried the NHS one and it put him as "very overweight" and in the 99th centile for his age. It was an American one I used before which said 99th centile, BMI 20.4 and obese.
He is fairly active, I suppose we must still be over feeding him. He doesn't get chocolate or crisps from us and now only occasionally from grandparents. They were slow to come on board though, so maybe he will lose a bit more now.
MIL made him SEVEN chicken goujons a few weeks ago (plus chips) and looked at me like I was crazy when I took them off his plate. Not even nuggets, actual goujons. We are usually with him when he is there for dinner thankfully.
Will keep trying anyway, thanks for the advice guys.