My 5 year old son is similar. My older kids will eat a range of food. The eldest won’t touch food when she’s not hungry or eat beyond satiety and I think has a pretty healthy attitude to food. I see myself in my middle son – he loves all kinds of food, he says he’s hungry right after big meals and eats and eats and eats. He admits sometimes he’s not hungry – just wants ” something yummy”. He’s probably my most robust, healthy, energetic child and he isn’t overweight.
Unlike your 6 year old, my 5 year old wont touch fruit in any form whatsoever. He doesn’t like cake or dairy desserts except icecream. He hates meat, picks the cheese off pizza & just eats the base. If we are eating fruit or yogurt near him, he makes us move away and can’t look at it. He eats loads of raw vegetables (even cauliflower) and cooked vegetables including soups. It was soon after I stopped breast feeding him (when he was 3) that I started GAPS/WAPF and wonder if that has affected him, though I always let the kids have a much more watered down version of the diet. He is pretty small for his age, pasty, has bad teeth and just not as robust as I’d like him to be but all the usual calorie dense enticements don’t seem to appeal to him and I don’t want to make him eat but he seems to live on air. He doesn’t get sick a lot and he has energy but he doesn’t look well! He has a lot of serious (as in anaphylactic reactions) allergies to foods, so I wonder if that makes food scarey for him. I think I need to honour his choices in food even though they may be very different to what I like, if he’s left to choose, maybe he’s making the right choices for his body even if his diet looks nothing like it’s “supposed” to. He also has tantrums and I think it’s due possibly to low blood sugar from not recognising he has to stop what he’s doing and eat!while I want to teach him self care I don’t want to over-ride his own mechanisms but its hard not to when it looks like they’re not working too well for him!