The science is settled, but like everything else, untrained people can't tell the difference between a good study and a bad study, and the media reports on them all.
Check out the book _How Not to Diet_, which is the most recent masterwork on evidence-based nutrition.
It doesn't take a domain expert to know this claim is fundamentally wrong. Science is never settled. There are conclusions that stand the test of time and accumulated evidence, but nutrition is a field with precious few of those.
The science is settled, but like everything else, untrained people can't tell the difference between a good study and a bad study, and the media reports on them all.
Check out the book _How Not to Diet_, which is the most recent masterwork on evidence-based nutrition.