I can relate to the overnight weight gain from too many carbs or too much sodium, then losing it over the following week. But what causes an overnight weight gain in the absence of carb or sodium? And when not premenstrual? And why won't it go away after 2 weeks? I have had outs of fluid retention that goes away within a week. I have not had weight gains (following the program strictly) inexplicably -- that refuses to go away? Temporary weight gain I understand. Permanent weight gain I do not understand.