Oh, come on! Somehow, the children who eat similar meals around here are supposed to be taking in radically different calorie counts. Middle child has just been given the news that she needs to be eating 3200-4000 calories (good stuff--- not junk foods) per day by her doctor as part of her summer training program. The Boy and Little Bit do not need extra calories because each of them has enough extra weight to facilitate even a super-dee-duper growth spurt.
The only things I can think of to make this happen, without fueling unnecessary weight gain by the siblings, are beans. The eldest and youngest find beans in all their glorious high-protein, low fat forms to be disgusting. Middle child loves, loves, loves beans. And she won't be in school where the, ahem, after effects of the magical fruit will get one nicknames having to do with toots. *sigh* There are bound to be other foods that will help our growing girl to build muscle and put on the weight she needs without packing on the pounds for her siblings. I just cannot think of any others right off the top of my head.
I think we should stop talking to doctors about weight.