Does a patient with 22 lbs to lose even need nourishment? Or just hydration and electrolytes? Sugar is just empty calories, so I wouldn't even call that "nourishment" and it will make you hungrier than fasting. I realize you were just following doctor's orders, but I don't think their orders have any rational basis and are just dogma. In fact, fasting and drinking sugar-free homemade electrolytes will actually facilitate accessing your 22-lb on-board pantry so that your body can nourish itself before, during and after surgery.

Since going low-carb with extra sodium, potassium & magnesium I never get cramps, even after long hikes in the Rocky Mountains. But when I go offtrack and eat sweet junk (very rarely), I will wake up in the middle of the night with excruciating plantar fasciitis (cramps in foot arches) and calf cramps that take at least 15 minutes to knead and walk out. For me it is a 1:1 correlation. I have no clue how sugar causes foot cramps, but there must be a mechanism for there to be such a strong correlation, for me, at least. I wonder if it can somehow bind magnesium, keeping it from my muscles, since Epsom salt baths seem to help.