Probably some combination of the two. The "science" around diet and exercise is thoroughly corrupted by huge amounts of money from various companies and people

Probably some combination of the two. The "science" around diet and exercise is thoroughly corrupted by huge amounts of money from various companies and people that try to push the results in directions to benefit themselves. Even the valid and reproducible studies out there seem to be twisted into into overly hyperbolic claims by companies looking for profit or bloggers/journalists looking for views.