[pessimizer]

That was the first study mentioned, solely for the purpose of confirming nutrition loss and not for the authors' speculations about causes. The next study was the Australian one cited to confirm protein loss.

If you want to know where they drew the statements about causes from, you might check the next three studies which, like the first two, are directly cited and linked within the text of the article.

But that probably wouldn't make a good comment, though.

[refurb]

"and not for the authors' speculations about causes"

I'm sorry? You're taking NatGeo's word over the people who did the research because, "the authors were just speculating?"

That's not how research works. That's not how any of this works.