What did Dr. Owen and Dr. Cahill do? Why was this so important?

In the late 1960's, Drs. Oliver Owen and George Cahill did one of the fundamental experiments in brain metabolism. (Mea culpa-- I identified Dr. Owen as Robert Owen mistakenly, now corrected). They measured what the brain required, macronutrient-wise, and how much of it was needed per day. In particular, patients who were morbidly obese were hospitalized and placed on a zero calorie diet for six weeks for the purpose of weight loss. The patients received adequate hydration and vitamins and minerals, but that was all. Unsurprisingly the patients lost weight. 

But what Owen and Cahill also did is now the stuff of legend. They catheterized both carotid arteries (the arteries that supply the brain with blood flow) as well as the jugular veins (that take blood away from the brain toward the heart). And they measured blood nutrient levels in both blood vessels to determine, from the differences in concentrations, what the brain actually extracted from the blood.

They found that the initial blood specimens, performed under the patients' usual dietary intake circumstances (high carbohydrate), demonstrated that the brain utilized about 130 grams of glucose per day. 

After six weeks of fasting, they found that the patients were fine mentally and emotionally (they tested them in a variety of ways) but their brain now utilized about 1/3 of the glucose compared with before. 2/3 of the brain's needs were now supplied by betahydroxybutyrate, the principle blood ketone body.

In short the brain had adapted to starvation, the most basic of ketogenic diets, and was fine.

Their data, after publication, were immediately misinterpreted by the American Institute of Medicine to say that the brain required 130 grams of glucose per day. Of course, this is exactly what they did not show, as the brain functioned perfectly well with 2/3 of its nutrient supply delivered as ketone bodies.

Sadly (and still mysteriously to me) the AIM's misinterpretation took hold with the traditional dietary community of the time and became a foundation principle of the low fat (high carb) paradigm. It's only now that we're seeing cracks form in that foundation.

An interested supporter, in a comment, was good enough to provide the complete reference for those interested in reading the original classic. I was remiss in not providing the ref, so much thanks:

Owen, O.E., Morgan, A.P., Kemp, H.G., Sullivan, J.M., Herrera, M.G. and Cahill Jr, G.F., 1967. Brain metabolism during fasting. Journal of Clinical Investigation, 46(10), p.1589. Doi: http://dx.doi.org/10.1172%2FJC...