You can't compare the two.
Many indigenous peoples show huge rates of obesity, hypertension and diabetes when following "typical western" diets. There has been some good research done in Papua New Guinea regarding diabetes rates as compared between islanders who have stayed native and those who have moved to cities. The second group tends to have dramatically higher rates of all nutrition related comorbidities.
The belief is that this has something to do with "thrifty genes" in regards to fat storage. For people with this genotype the prevalence of calorically dense, cheap foods is pretty much a gaurantee of nutrition related disease.
The diet of arctic circle dwellers is atypical of indigenous populations as the sort of gatherer/agriculturalist food patterns that austronesians, american indians etc. practiced (and still practice in some cases) are not possible at high degrees of latitude.
The 80% fat diet would be very specific to people who primarily get calories from whales, seals, fish and caribou and reindeer where available with little to no carbohydrate intake whatsoever.
This is opposed to more typical mid and low latitude indigenous groups who eat a variety of staple foods including game, tubers, fruit and some vegetables. Typical indigenous diets in all cases are probably lower in calories than modern western diets. Neither example display obesity comorbidities in high numbers without access to cheap, modern diets.
The 80% fat diet works very well for the small groups of people that practice it. They do so eating foods that are completely unavailable, often due to legal restrictions outside of the arctic circle (whale blubber anyone?). Their traditional foods are not only high in fat but very high in vitamins and minerals, and while calorically dense are limited in total availability. Those people are also genetically adapted to a very specialized diet.