I'm not that knowledgeable on the subject , but what you see here is called a ketogenic diet ie. one that burns fat , rather than sugar. And what you said , for the Ukrainians is just as you've stated , the fat they eat is natural , healthy , without additives , basically they are having a normal diet, not a fabricated one. Here is a video i watched a few hours ago, just information for the ketogenic diet, ince I'm looking into the subject

And also I would Love it if you take a look at my second post , it's on Training , so it might be helpful. There is another video there about the benefits of exercise for the brain and the detrimental effects of sugar and slouching around.
https://steemit.com/story/@j3dy/answer-to-life-challenge30-day2-train-and-think-or-steemit-review