I was shocked by the 9 year old boy who weighed 3.5 stone.
As that is a NORMAL weight (low but not too low)! Boys that age are often skinny, if they are active, and not naturally that bothered by food.
I have an almost 9 year old with that weight, he looks very thin, and I used to worry about it until my GP told me that with children this age you are actually supposed to see their ribs, and that he is ver healthy.
And about fussy eaters, some children really are BORN fussy. My DS2 was hard to wean as he refused bottles, from a very young age (we tried when he was 1 week, 1 month, 3 months, just to give me a break. didn't work) and refused formula. once he was 6 month old, he ate fresh food but refused the jars of babyfood. Right now he won't have milk if it is not very very fresh (I cannot fool him, he can tell milk is a bit off before it actually is IYSWIM). etc etc. really, he was born this way, he just has a very (overly?) sensitive palate...it happens.
I find that people who do not have fussy eaters claim it is their superior parenting
when really it is the luck of the draw.