Does water depletion mess up your body's electrolyte balance? That is what I have been told.
Last year after I did a week long water depletion for a contest I woke up screaming every night for three months because of the horrible cramps in my legs and feet. My doctor told me that was the reason.
I did the standard no salt, no carbs, rinse your tuna, drink only distilled water and increase to 10 liters a day, then cut out water completely on the last day and take some natural diuretics.
If that was what caused the leg cramps I would not recommend it to anyone.