Health & Nutrition by Michael R. Eades, M.D. » Metabolism and ketosis

Health & Nutrition by Michael R. Eades, M.D. » Metabolism and ketosis: "But the breakdown of muscle creates another problem, namely, that (in Paleolithic times and before) survival was dependent upon our being able to hunt down other animals and/or forage for plant foods. It makes it tough to do this if a lot of muscle is being converted into glucose and your muscle mass is dwindling.
The metabolic system is then presented with two problems: 1) getting glucose for the glucose-dependent tissues; and 2) maintaining as much muscle mass as possible to allow hunting and foraging to continue.
Early on, the metabolic system doesn’t know that the starvation is going to go on for a day or for a week or two weeks. At first it plunders the muscle to get its sugar. And remember from a past post that a normal blood sugar represents only about a teaspoon of sugar dissolved in the entire blood volume, so keeping the blood sugar normal for a day or so doesn’t require a whole lot of muscular sacrifice. If we figure that an average person requires about 200 grams of sugar per day to meet all the needs of the glucose-dependent tissues, we’re looking at about maybe a third of a pound of muscle per day, which isn’t all that big a deal over the first day. But we wouldn’t want it to continue. If we could reduce that amount and allow our muscle mass to last as long as possible it would be a help."