I looked into some of his specific claims. Even if dry fasting is legit, the evidence and references its proponents cite are often twisted or based on pure conjecture and unreasonable extrapolation of basic physiological fatcs.
“When we fast our body creates water primarily as a byproduct of the fat we are burning. Hydrogen released from the metabolized fat combines with oxygen from air and creates h2o"
Estimated that every day the body is able to produce a liter of metabolized water in this way, and freshly synthesized water is believed to be much more pure than water consumed from the outside because it is free of toxins found in water we drink”
- 110 grams (=mL) of water is released for 100g of Fat, so you would need to burn 1000g of fat, or 7600kCal for 1L of water, which we know does not happen.
From “Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate”, MN Sawka - 2005 - dtic.mil;
"… water production is an average of approximately 250 to 350 (m)L/day for sedentary persons—but which can increase to 500 to 600 mL/ day for physically active persons (Hoyt and Honig, 1996). Hence, respiratory water losses are roughly equivalent to, or offset by, metabolic water production (Table 4-2; Hoyt and Honig, 1996)"
and from: National Research Council. 2003. “Nutrient Requirements of Nonhuman Primates”: Second Revised Edition. Washington, DC: The National Academies Press. https://doi.org/10.17226/9826.
“… The gross yield of metabolic water from oxidation of 100 g of carbohydrate, protein, and fat is about 60, 41, and 107 g, respectively (Askew, 1996). However, excretion of the urea produced during protein oxidation requires nearly all the metabolic water released. Thus, there is no net water yield from oxidation of protein. Metabolic water furnishes about 8-10% of the water needs of humans (Askew, 1996)… Metabolic water is also generated during muscular activity through catabolism of stored glycogen and fat. However, the anaerobic metabolism of glucose to lactate (associated with intense effort) yields only one-third as much water as does complete glucose oxidation, and the metabolic-water contribution from either anaerobic or aerobic effort is still a small proportion of total body water (Askew, 1996).”
Clearly showing that the generated water is likely a net zero, as it equals the amount you lose by evaporation, and what comes from proteins is used to flush out urea. That leaves a deficit equal to the volume of water body needs for anything else, which includes thermoregulation, osmoregulation and regulating the blood volume etc. Also mind you that he is exaggerating and not providing any proper references, in addition to the nonsensical claims about they purity and the toxins etc.