Good deal, Biff. (Totally love this stuff.)
Richard has a nice post here: Dr. Phinney's take on fasting (Good thread, overall, too.)
What really makes sense to me is that the more body fat we have, the less likely we are to burn good lean tissue. If one is down close to the normal lower limits on body fat, then if the body feels that “starvation” is the deal, and that it needs to burn lean tissue to keep the brain, heart, liver, lungs, kidneys, etc. going, then yes - it’s going to do it.
I picture it as an exponential deal where LBM loss is zero or close to it when very substantially overweight, negligible when moderately overweight, and then really ramping up as one approaches 4 to 10% body fat for men, and 10 to 20% for women. I’m picking the lower end of those ranges as where it’s “essential fat” that’s necessary for the proper physiological operation of our bodies.
I listened to Dr. Phinney’s presentation, and he says that after so many days (30?) the lean body mass loss declines to 1/3 lb. per day, whereas it starts out at 3/4 lb. per day on the 2nd or 3rd day of a fast.
There must be further moderation of this, or else it’s not entirely healthy muscle mass. Consider the guy who fasted for 382 days, going from 456 lbs. to 180 lbs. Never have seen anything to indicate he had lost valuable lean mass or was in any way “lacking in muscle” at 180 lbs.
@ron-coleman fasted for 46 days, and @JorgePasada went 60 days, and I didn’t see any concern or mention of LBM losses that were of any concern.
I’ve lost 50 lbs. with a lot of fasting, anywhere from 1 day to 5 days, over the past 5 months, and while I’ve never had any body scans, etc., for lean mass, my grip strength is exactly the same, as measured by the ‘Captains of Crush’ grippers that I’ve got. More subjectively, once in a while I lift heavy and awkward stuff in the course of my job, gas cylinders, our own equipment, etc., stuff in the 110-160 lb. range, and I feel the same as ever.