Who uses a certain (previously uncommon) diet that is said to help with diabetes and other serious issues? Those who are of average good health or those who experience some issues that already start to manifest? I wonder if the study corrects for those factors. Does the average person even participate in those studies?

We really need multiple long-running (50+ years) randomized study that controls for all influence factors to really answer the questions. Something that is unlikely to be accomplished in our current political lifetime and unlikely to be completed within our lifetime.