Fascinating. Also entirely consistent with genetic determinism by the usual natural selection story - 9 year olds who survive starvation have bad-ass genes, etc.
If it was just selection, the effect wouldn't be as strong, and should happen regardless what age the starvation happens.
Re: 'regardless of age': you can't rule out genes that influence near-starvation thrive/fail differentially at young vs teen ages. Nevertheless I agree that this is suggestive evidence for "it's not just regular genetics". Good analysis if it indeed applies to this case!