I have read the "de-bunking" that plant positive did concerning the research done on Stefansson and his Inuit diet and they neglect to point out that the initial diet was high in protein and very lean and this did caused health issues because a high protein diet is not healthy. In the absence of fuel (fats and carbs) the liver will convert proteins into glycogen which is both stressful to the body and inefficient because of the conversion of protein to energy is less than 90%.
When he and his partner modified the test diet and increased the fat intake and ate a very limited amount of carbs (vegetables) they were fine.
After this Stefansson re-joined the world and adopted a more western diet and many of the health issues he had experienced prior to his time with the Inuit returned.
My mother in law (65 years old) has had chronic pain issues for years... she has recently adopted a lower carb, higher fat diet which is very much like her mom used to make aside from cutting out bread / grains.
Her pain levels have dropped, she sleeps better, and now is seeing some extra weight coming off... my father in law is not complaining as his wife gets curvier and more importantly, has more energy to do things like going snow-shoeing in northern Michigan.
She is also enjoying some guilt free eating and has a much richer diet and expect that my father in law (diabetic) will soon be onboard with this as he battles with weight issues and diabetes is common in his family (he is from the deep south).
It does not take a radical change in one's diet to see improvements, whether you go low carb / high fat (omnivore) or vegan / vegetarian the common thing I see with people who get healthier is the elimination of processed foods and sugars and in either case, most people need to increase their fat intake as this greatly aids in the absorption of nutrients you get in all those vegetables.
If it is a matter of weight loss being a goal, lowering your carbs is the only way to go but one should avoid starvation so you have to change the fuel source... for vegans things like coconut oil, olive oil, nuts, and avocado are some excellent options to increase dietary fat.
This is hard science btw...