Actually I believe alcohol is the preferred source LOL. Your body will burn alcohol calories before any other calories can be used.
In animal studies we use the word 'preferred' to mean whatever the animal will eat first, or in preference to other foods that are offered at the same time. Using this criteria, glucose is unquestionably the preferred fuel in humans (after alcohol) whether they are in ketosis or not, and whether they are underfed or overfed. Your body MUST deal with blood glucose in a timely and efficient manner or else you will be very ill/dead. All other macronutrients can wait to be dealt with to a certain extent.
In animal studies we use the word 'preferred' to mean whatever the animal will eat first, or in preference to other foods that are offered at the same time. Using this criteria, glucose is unquestionably the preferred fuel in humans (after alcohol) whether they are in ketosis or not, and whether they are underfed or overfed. Your body MUST deal with blood glucose in a timely and efficient manner or else you will be very ill/dead. All other macronutrients can wait to be dealt with to a certain extent.