A very important difference is that you can't drink water during a Ramadan fast. Regardless of what you're doing with your food, deliberately dehydrating yourself is pretty much never justified.
The body produces water as a byproduct of ATP (energy) metabolism. During a fast, fat and other tissues are broken down by catabolic reactions to accomplish this. Knowing this, I am willing to entertain the idea that abstaining from water for a period of time can be beneficial, or perhaps I should say at least not harmful, because there are mechanisms in the body that synthesize water. Obviously, a sufficiently long period of time without water would be harmful.
I haven't done the math to figure out how much water this is, and so I do not know how sufficient it is to keep minimally hydrated during a water-fast. I'm just saying that the thought of abstaining from water during a fast isn't necessarily as dangerous as it sounds, because your body can and does produce it's own water as a by-product of energy metabolism.
Yes, because they selected subjects who were observing Ramadan and that makes their study easier to carry out. My point is that the dehydration is counterproductive.
Exactly. Maybe I wasn't clear in my comment above. My point is that most resources on intermittent fasting allow (and actually encourage) drinking a lot of water, and rightfully so. At the same time a lot of the research is done on subjects who observe Ramadan fasting and do not drink water. This difference has to influence the results in some way.
I think the logical interpretation of GP is that it's never justified from the perspective of physical health. Whether religious obligations outweigh ones health is a completely personal decision that no outsider gets any say in.
