People who never experimented themselves with nutrition do not understand the limitations of these studies. They only look for one effect for a relative short period of time. So not only they might miss other side effects but also they conclude based on the shock effect major changes have on your body. But once these changes become normal the body adapts and the effects might go completely away.

From my personal experience: very high protein with calorie deficit can allow you to build muscle while losing fat but also causes impotence, anxiety, poop so hard you scrape your insides till you fill the toilet with blood. Are the studies right? Yes. Do you want to follow their advice? Not really.