I was a fussy eater, because I came from a neglectful home and was fed on junk and sweets, so noway was I going to welcome vegetables at a strange house. This continued until into my 30's.
My DD has a limited diet because of Autism. She would starve herself, if forced into eating. As for the comments about the children in poor countries, it wouldn't go down well with SS if you allowed your child to be malnourished because you wanted to dictate what they ate.
"but that limited diet doesn't seem to include crisps, fish fingers and other frozen junk food, chocolate and sweets."
When you consider the effect these foods have on the brain, it makes sense that a child with limited food choices would choose them to eat. Many perfectly functioning/rational Adults are addicted to their diet, we can't expect better from children.
My toddler Granddaughter has food issues, which is connected to toileting. It would be unbelievable to many on here how little she eats. She would be ill if she wasn't offered what she will eat and yes, that includes Wotsits.
Humans are very good at getting what they need from their diet, so why people get so hung up about food that they can't feed a child one meal, every now and again, that doesn't include every food group, i don't understand, because there isn't any reason to.
My children are Adults, all of their peer group have sorted their eating out enough so they are not going to drop dead at 50, or it mean they can never eat out.
The only reason to get annoyed with a fussy eater is if they are trying to dictate were you eat out etc.