Every food commercial, advertisement, and packaging in the US is currently protein obsessed. I just bought 3 burritos, and the most noticeable thing on the entire package is its protein content. TV commercials about waffles are advertising that they have X amount of protein per serving. The products in my jobsite’s vending machine have protein all over every package.
Did America have a protein thing recently?
Of course there is little research on the zero carb diet. There are few people using it. The only stuff I’m aware of is on the specific health problems the diet seems to fix, the only controlled study I know of was on the heart health impacts of the diet (people on zero carb who exercise a lot have very high LDL cholesterol. We now know that cholesterol in that population is not associated with cardiac plaques)
Studies are rare because nearly no one follows the diet so governments don’t care, there’s no money from the meat industry for diet science, and unlike plant based diets there’s no large religion promoting the diet.