They call them "controlled trials" but they are anything but. Actually take the time to read them in detail and you'll find, almost invariably, long term surveys based on people who said they were "going to make X change to their diet."
I don't mean to be insulting, but I think it's quite naive myself to just think that the same academia culture that produced the "science" that we should stop eating saturated fats and animal based foods because they will kill us, and instead eat a bunch of motor oil, inflammatory grains, and insulin spiking carbs and sugars... maybe they don't have the perspective (or independent thought) necessary to even begin to make an honest assessment of something they are certain is bad before even beginning?
If you have a "controlled trial" that you think is better than what i described above, I'm happy to save it in my resources to dig into later. Feel free to share any that you think are actually solid & honest explorations of diet.