"She's not eating properly"

our neighbour told me.
She was watching her younger grandchild attempting to turn cartwheels on our front lawn. The cartwheels were not wildly successful but the child and her sister were having fun.
"She's been off school for ten days being treated for constipation."
I waited for some more. I knew I'd get the details.
To my mind neither of the girls eat properly - not for want of trying on their grandmother's part. The sort of food we ate as kittens doesn't seem to be considered "normal" now.
I know things have changed. Pizza was unknown when I was young. There was one sort of lettuce - iceberg. We didn't know what "broccoli" was - although we certainly knew "cauliflower". A zucchini/courgette didn't appear on the table until I was in my teens - and it was "new" to most people then.  We had never had a "stir-fry" and fish always came fried in batter.
Compared with the modern child our diets were really rather monotonous and boring - stew, mince, chops, roast, fish on Fridays (even if you weren't Catholic), the very occasional BBQ at a picnic, and chicken at Christmas. 
We ate it all - largely without complaint and with voracious appetites. The holes were filled with fruit and, occasionally, slices of bread or "weetbix" and the Downunder version of Marmite known as "Vegemite". We rarely had jam - and if we did it was homemade. We drank water and milk. Lemonade was something we had on Christmas Day. Ice cream was a treat.
I know our diet has changed - and changed for the better. So why should a small kitten from a good middle class family with well educated parents not be eating properly and suffering the consequences? I know she isn't the only one. Her sister is rather the same. There are other children I know that age. They "won't eat" this or that or something else. 
Middle Cat's children ate almost everything which was put in front of them. There are a couple of things they really didn't like. They tried them because they were told they must at least try but she didn't force them because there were sensible alternatives. They were told, "If you really, really don't like that then you must eat this instead." She explained why.
She found time to do it even though she was working full time. Perhaps it helped that their paternal grandmother was a superb cook of Greek-Cypriot origin? She knew how to feed small children - and big ones too. 
My brother's children were a little "fussier" but they ate most things. My niece and her husband resorted to one of the best encouragements ever. They have had their three girls grow some of their own food.
But these other two kittens and too many more like them "don't like" this and that and the other thing. They seem healthy enough but I wonder what nutrients they are missing out on and what effect it will have in later life. 
I know another child too. She is on a restricted range of foods because of a life-threatening medical condition.  She is now old enough to be aware of what she can and cannot eat. We were talking about this and she said
     "Maybe their mum should just tell them they can't eat all the things which are good for them because you know something I'd really, really like to try all those things they don't want to try."
It's a thought - but I suspect it's a bit late now.