There's a lot to be learned from the Kitava study. Kitavans eat a diet of root vegetables, coconut, fruit, vegetables and fish and have undetectable levels of cardiovascular disease (CVD), stroke and overweight. Despite light smoking. 69% of their calories come from carbohydrate, 21% from fat and 10% from protein. This is essentially a carbohydrate-heavy version of what our paleolithic ancestors ate. They also get lots of sunshine and have a moderately high activity level.
The first thing we can say is that a high intake of carbohydrate is not enough, by itself, to cause overweight or the diseases of civilization. It's also not enough to cause insulin resistance. I sent an e-mail to Dr. Lindeberg asking if his group had measured Kitavans' glucose tolerance. He told me they had not. However, I can only guess they had good glucose control since they suffered from none of the complications of unmanaged diabetes.
The Kitavan diet is low in fat, and most of the fat they eat is saturated because it comes from coconuts. Compared to Americans and Swedes, they have a high intake of saturated fat. So much for the theory that saturated fat causes CVD... They also have a relatively high intake of fish fat, at 4g per day. This gives them a high ratio of omega-3 to omega-6 fatty acids, with plenty of DHA and EPA.
Their blood lipid profile is not what a mainstream cardiologist would expect. In fact, it's "worse" than the Swedish profile in many ways, despite the fact that Swedes are highly prone to CVD. This raises the possibility that blood lipids are not causing CVD, but are simply markers of diet and lifestyle factors. That's very easy for me to swallow because it never made sense to me that our livers would try to kill us by secreting triglycerides and withholding HDL. The blood lipid profile that associates best with CVD and metabolic syndrome in the West (but has no relation to them on Kitava) is one that's consistent with a high carbohydrate intake. Where does carbohydrate come from in the West? White flour and sugar maybe?
Kitavans also have very low serum leptin. This may be a keystone to their leanness and health. It suggests that their diet is not interfering with the body's metabolic feedback loops that maintain leanness.
The Kitavan diet is one path to vibrant health. Like many other non-industrial groups, Kitavans eat whole, natural foods that are broadly consistent with what our hunter-gatherer ancestors would have eaten. It amazes me that as humans, we can live well on diets that range from near-complete carnivory to plant-rich omnivory. We are possibly the most adaptable species on the planet.
The ideal diet for humans includes a lot of possibilities. I believe the focus on macronutrients is misguided. There are examples of cultures that were/are healthy eating high-fat diets, high-carbohydrate diets and everything in between. What they do not eat is processed grains, particularly wheat, refined sugar, industrially processed seed oils and other modern foods. I believe these are unhealthy, and this is visible in the trail of destruction they have left around the globe. Its traces can be found in the Pacific islands, where close genetic relatives of the Kitavans have become morbidly obese and unhealthy on a processed-food diet.