I wouldn't necessarily be so quick to knee-jerk throw out that technique. Perhaps it's like BMI where it's an approach that's completely inappropriate for assessing an individual, but when applied to a population its shortcomings average out in a way that lets it serve as a valid statistical tool for certain purposes.
I think the real story here is illustrated in the contrast between that last section that you mention, and how many folks are reacting to this study: The actual science is full of nuances and caveats which experts in the field are expected to understand, and like literally any scientific paper its results should be considered tentative unless and until it's been corroborated by further research, including research that uses different protocols. The public reaction, on the other hand, treats this as if it should be a cut-and-dry statement on a black-and-white issue.
> like literally any scientific paper its results should be considered tentative unless and until it's been corroborated by further research, including research that uses different protocols
To expand, this study is interesting in that it opens an avenue for further investigation. It's like learning an extra person was at the scene of crime. It proves nothing, and doesn't even necessarily SUGGEST anything. It's just another "lead" that researchers should investigate.
In this case, it doesn't help that the additional "suspect" is something sexy like protein-rich diets.
> The public reaction, on the other hand, treats this as if it should be a cut-and-dry statement on a black-and-white issue.
That's because the public as a whole usually wants cut-and-dry statements and black-and-white issues. And the news caters to the public.
I think the real story here is illustrated in the contrast between that last section that you mention, and how many folks are reacting to this study: The actual science is full of nuances and caveats which experts in the field are expected to understand, and like literally any scientific paper its results should be considered tentative unless and until it's been corroborated by further research, including research that uses different protocols. The public reaction, on the other hand, treats this as if it should be a cut-and-dry statement on a black-and-white issue.