"Bed rest conserves energy to the max' extent possible, to devote this energy to cleansing and healing exclusively, rather than waste any on activity or emotional involvement; this is also apparent in the wild where fasting animals will hardly move except to obtain water for survival.
So most of Sheltons practices were based on Nature and what happens in Nature rather than anything else."
I agree that with severe injury or sickness bed rest is very appropriate, but it certainly does not apply to 'regular', far more frequent kind of fasting, to which all creatures, large and small, are accustomed as an integral part of their reality on this planet.
Speaking about what is natural, a starving animal in the wild MUST move or it will perish. The same turns out to be true about fasting lab rats. Studies show that when forced to fast, they increase their physical activity by up to 50% compared to the fed rats.
It so happens that healthy people also tend to increase their phys. activity when fasting. Some even report that they start _craving_ movement at the onset of a fast. On the Russian fasting forum the regulars pump iron and run miles during their fasts. All report that doing so makes fasting so much more pleasurable and effective.
In the old Soviet clinics bed rest was permitted only in the first days of refeeding. A patient was required to walk 5 miles a day, weather permitting, and a refusal to get out of bed was the grounds for dismissal. The Russians have long established that physical activity is essential during a fast -- and they certainly fasted tens of thousands!
Shelton's insistence on bed rest flies in the face of the fact that people feel much better during a fast if they are physically active.
"Inactivity will produce muscle wastage while eating, but while fasting, muscle is greatly preserved through something known as "protein-sparing", so you are incorrect on that score."
On what exactly do you base this? Fasting will _always_ catabolize some muscle; this is a well-established fact. While I am not aware of the studies that actually tested this on humans, the anecdotal reports of experienced fasters echo the 'use it or loose it' adage. People claim that they loose less muscle bulk if they exercise during a fast. It also stands to reason that, when in need, the body will try to preserve what is currently in use and avail itself freely of what is not.
Besides, phys. activity upregulates mitochondrial function, making the production and utilization of energy more efficient. In addition, during a fast, blood Sugar rises in response to exercise -- and not because more muscle is catabolized but because lactic acid is recycled in the Cori cycle, lessening the demand on gluconeogenesis.
You wrote that gym, sauna and colonics are a waste of time and that fasting clinics "use these as a justification for the expense of staying there". The experience of people who fasted with and without all this says otherwise. Fasting clinics offer all this, because people demand it; and people demand it because this is what makes a difference between a miserable experience and a pleasant one.
The topic of enemas and especially your statement that "autolysis will use impacted feces as fuel during a fast" demands a post of its own. I will address it later.
As for the studies on PubMed, I can't just refer you to particular ones, because I've read hundreds, starting with George Cahill and Oliver Owen in the 1960s through the 2000s. That mainly dealt with the specifics of the metabolism "of starvation" as fasting was usually referred to in Science then. Then I read most of the papers that quoted Cahill and Owen and then those who quoted most interesting of those in turn. Some notable names are Richard Veech, Anna Maria Cuervo, Cintia Kenyon, Valter Longo. I read all that, because I could not find good info on fasting anywhere.