Those "hunger strikers" weren't fasting because they were being force-fed. Ancel Keys' Minnesota "starvation" studies students also weren't fasting, they were on low calorie diets. None of these people were allowed to become fat adapted, where one can actually make glucose from fat. http://chrismasterjohnphd.com/2012/...ose-from-fatty/
If you get force-fed through the nose or are fed 500-1000 calories of SAD in a ward study, you will never become fat adapted, so you will use up all your blood glucose, then glycogen, then use protein to make glucose.

From some of the cited articles in Fung's books, true fasting with zero or close to zero carbs, kicks in other body-saving pathways like increasing human growth hormone production on day 2-3 and reducing insulin resistance. This amps up autophagy where the body breaks down decrepit cells but conserves and reuses pieces to build new protein molecules (moreso than when you are eating protein so the body doesn't bother to conserve it). Fasters who have been closely monitored don't lose muscle until they get below 4% body fat. In fact, some gained a pound or two of lean body mass during 30-90 day fasts.