The Inuit were healthy on an almost all-animal diet
The early reports of low heart disease among the Inuit rested on thin data, and later reviews found rates similar to other populations, with high stroke rates. Their diet also has unusual features, such as marine fats, organ meats and some genetic adaptation. Even if it were healthy, it would show that one diet can sustain people in the Arctic, not that a well-planned plant diet is harmful where plants are available.
For thousands of years the Inuit lived in a place with almost no plant food, eating mostly seal, whale, fish and caribou. By most accounts they were not sick in the ways modern Westerners are. Their health got worse only as sugar, flour and processed food arrived. That suggests a diet built almost entirely on animal foods can support human health, and that plants are not the indispensable foundation they are often made out to be.
The health picture is weaker than it looks. The famous claim that the Inuit had little heart disease grew out of 1970s work on Greenlandic Inuit. That work measured fats in the diet and estimated heart disease from records that were patchy in remote settlements. A 2014 review of the evidence found that coronary disease among Inuit was broadly similar to rates in non-Inuit populations, and that stroke was more common. Studies of frozen and preserved remains of Inuit who died before Western contact have found hardened arteries. Life expectancy in traditional Arctic communities was also short, for many reasons. That makes long-term disease hard to judge either way.
The diet was also not just meat. It was built on seal, whale and fish, which are rich in long-chain omega-3. It included organ meats and raw or lightly cooked flesh, which supply vitamin C and other nutrients that muscle meat alone lacks badly. And there is genetic evidence of adaptation. Inuit populations carry variants affecting fat metabolism that are rare elsewhere. So results from this group do not carry over neatly to a European or North American eating beef and chicken.
The rise in disease as Inuit communities took up a Western diet is real. That diet brought sugar, refined flour, alcohol, smoking and much less physical work. That tells you processed Western food is harmful. It does not tell you which of the two older diets, Arctic animal-based or plant-based, is better.
The bigger point is what the example can and cannot show. People surviving and doing reasonably well on the food available in the Arctic shows that humans are adaptable. It is not evidence against plant-based eating. Large cohort studies and the major dietetic associations find that well-planned vegan diets are adequate and linked with lower rates of heart disease and type 2 diabetes. A population with no access to plants had good reason to eat as it did. Most people raising this example are not in that position.
Drawing a general conclusion from a sample too small or too unrepresentative to support it.
How it applies here: Draws a conclusion about humans in general from one population. That population ate a distinctive marine and organ-meat diet, carries genetic adaptations to it, and was studied with unreliable early health data. The finding is then applied to people eating very different animal foods in very different conditions.