I read an article a while back about the traditional Native American diet, it definitely made me think about this idea, considering the poor state of health of most Native Americans eating SAD. My family has some Cherokee heritage on my dad's side, and I often wonder if my lactose intolerance (and possibly gluten intolerance) stems from that lineage.
Guts and Grease: The Diet of Native Americans - Weston A Price Foundation
I think in the end it's all going to be about things like CAFO, processed, and added sugars. I was born in 1955 which means that while I ate CAFO chicken (which started in the 50s), beef and pork weren't CAFO until the 1970s, so I got to eat relatively healthy food through puberty. My grandparents didn't eat CAFO until they were already grandparents. I bring this up because in my family it was usual to live to be 85+ until my mother's generation. Coincidentally, that was the generation that fell in love with convenience foods like tv dinners, canned soups and sauces, etc. It also coincides with the proliferation of fast food places like McD and their ilk.
It's not scientific, but observationally, what I see is that the generations that ate tomato sauce made from tomatoes (not premade in a can), produce not shipped from 1500 miles away, real olive oil, homemade wine, and meats that weren't CAFO lived longer than the next generation. And they ate plenty of wheat in the form of pasta and doughs that stretched meat out for large families.
"I puked like a hero for the rest of the night," Anthony Bourdain, 2002. (After spending the day eating ant eggs, bugs, and larvae, and drinking some gelatinous alcoholic stuff.)
I would like to point out that, while not during the winter, Alaska has and abundance of vegetables, tubers, and berries that the Inuit would gather and eat during that time. The reason they need to eat so much fat, as I have discovered in my last year and a half of living up here, is because it is so damned cold. I found that the amount of fat I was eating down in Oklahoma was no-where near enough to what I needed up here. But I have also found that there is a LOT of foraging that I can do in my own back yard during the summer. You just have to know what you are looking for.