You mentioned a high-fat diet sometimes showing negative results in the context of low fiber. We know that traditional cultures ranged in their macronutrient ratios, and I believe some traditional cultures ate low-fiber diets. What do you think is the explanation for the contrast from an ancestral lens?

Chris Kresser:  I’m not aware of any traditional culture that ate a low-fiber diet, actually. The only one that comes to mind that is possibly lower, and this is not really a Paleolithic people, but it’s a pastoralist people, which is the Maasai who primarily consume fermented milk products and fresh milk and blood and meat from their cows, but they also consume some fiber-rich plant material. Most hunter-gatherers that have been studied, contemporary hunter-gatherers, actually had extremely high fiber intakes, as I think I mentioned in the presentation this week, sometimes upwards of 100 grams a day, which is just absolutely off the charts. If you start looking at what kind of food you’d have to eat in a day to get 100 grams of fiber, it’s pretty daunting. And so I actually, unless there’s a population that I’m not thinking of, don’t know of a population that had a very high fat intake with a very low fiber intake. Even if there were such a population and they were able to thrive, that doesn’t mean that we would thrive doing that.

The Inuit are often raised as an example of a people that thrive on a very-high-fat diet, but the Inuit are really an outlier. They ate that diet because they lived in an extremely marginalized environment, not because they wanted to or thought it was healthy. Whenever they could get their hands on any plant matter, they ate it, and there’s been a really interesting study a year or two ago that showed that traditional Inuit people have genes that change their biochemistry in a way that allows them to thrive on very high intakes of omega-3. Not everyone has these particular genes or expression of these genes, so that may explain why some of the studies that have looked at extremely high levels of EPA or DHA as a supplement have shown not only no benefit, but actually potential harm. We always have to be careful about extrapolating information from one particular population, particularly a population that lived in a marginal environment for a long period of time, and then saying that that applies to the general population.