" The “remarkable sodium and water retaining effect of concentrated carbohydrate food,” as the University of Wisconsin endocrinologist Edward Gordon called it, was then explained physiologically in the mid-1960s by Walter Bloom, who was studying fasting as an obesity treatment at Atlanta’s Piedmont Hospital, where he was director of research. As Bloom reported in the Archives of Internal Medicine and The American Journal of Clinical Nutrition, the water lost on carbohydrate-restricted diets is caused by a reversal of the sodium retention that takes place routinely when we eat carbohydrates. Eating carbohydrates prompts the kidneys to hold on to salt, rather than excrete it. The body then retains extra water to keep the sodium concentration of the blood constant. So, rather than having water retention caused by taking in more sodium, which is what theoretically happens when we eat more salt, carbohydrates cause us to retain water by inhibiting the excretion of the sodium that is already there. Removing carbohydrates from the diet works, in effect, just like the antihypertensive drugs known as diuretics, which cause the kidneys to excrete sodium, and water along with it. This "

― Gary Taubes , Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease