Actually, Eskimos eat or used to eat a diet of some 80% and they were healthy and had no weight problems and diabetes was virtually non-existent. I think some other cultures had very high fat diets as well.
Check out some of the books by science writer Gary Taubes' on the topic. Pretty interesting and goes opposite to what the mainstream media was saying, but they're starting to come around a little bit. At least some of them.
At least they got rid of the idiotic food pyramid that was the fruit of a vegetarian on Sen. George McGovern's staff. After the government endorsed that, over the objections of some doctors at the time, obesity and diabetes really started taking off.
https://blog.bulletproof.com/new-eat-more-fat-infographic-gary-taubes-why-we-get-fat-in-a-nutshell/
http://garytaubes.com/