Contrary to the recent past, when high carb - low fat diets were recommended, it appears that now the opposite type diet is often being recommended. Many doctors who have written books on the subject recommend diets high in fat and extremely low in carbohydrates, limiting them at 10% of caloric intake.
It is unclear how pragmatically one could live on just 10% carbohydrate. The latter represents the most efficient source of energy for the body. Athletic performance, endurance would suffer with only 10% carbohydrate.
I gather the idea of the high fat diet is to change the metabolic state of the body in a state of ketosis whereby given the absence of readily available carbohydrate fuel, the body learns how to use and burn fat for energy. Is this process all that healthy and sustainable over the long term? And, would it enhance cognitive capabilities over the long term as one ages.