For all of Phinney’s attributes, I’ve seen him over-generalize and project into the future in ways that are demonstrably untrue, i.e. his claims about how much needed lean tissue is lost, day-by-day, when fasting - witness the famous case of the guy who fasted for 382 days, and the accounts of fasting for 60 and 44 days on this forum.
I agree that autophagy can in theory be a double-edged sword, yet I think it’s alarmist to say,
“After just one day of fasting, you begin to lose body protein from lean tissue – from places like muscle, heart, liver, and kidneys. These organs and their functions are things that we want to preserve, and definitely should not be given up lightly. So while you may lose weight according to the scale, part of it will be at the cost of your important, metabolically active tissue.”
The guy who fasted for 382 days went from 456 lbs./207kg. to 180 lbs./82kg. and was fine, and maintained close to that final weight for years afterwards. It’s not like his heart muscle went away.
Totally agree that we excrete nitrogen during fasting, yet that does not necessarily mean that vital structures and cells are being harmed. Our skin accounts for almost one-sixth of our weight - right there is a huge source of “lean body mass” and as we lose skin that excreted nitrogen will show up. Losing skin while fasting definitely happens for many people. Not sure about what percentage of people this is true for, but there is a common theme of people who fast not having the loose/saggy skin as do many who lose weight by calorie restriction or other non-fasting means.
Hey, I’m in the 9th day of a fast right now, and I want to know. No doubt we “use stuff up” when fasting - the Noble Prize-winning work of Yoshinori Ohsumi and others proves it. Yet where is the science that actually says that fasting beyond 24 hours damages our organs?
A lack of autophagy - our cells not getting rid of pathogens like viruses and bacteria, damaged and diseased cellular components, and other harmful materials - is what leads to neurodegenerative diseases like Alzheimer’s and Parkinson’s. The breaking down of proteins into amino acid components is what our neurons do - otherwise the proteins become toxic, and autophagy is how they do it.
The above is my main disagreement. On slowing metabolism - I do believe that the body will “turn down the thermostat” to conserve energy, in the long run. However, here I am, fasting away, and my hands and feet are as warm as ever, and I’ve felt no sluggishness, tiredness, etc., of any kind.
Dr. Fung maintains that fasting does not result in the slowing of metabolism, as does calorie-reduced diets. For me, anyway (and thus far), that seems to be true.