When water balance is off due to prolonged dehydration or purging behaviors such as vomiting, laxative or diuretic abuse. When you have an inadequate protein intake in your diet. When the protein level in your blood goes too low, the colloidal osmotic pressure will decrease and allow fluid to escape into your tissues and cause edema - swelling of the hands, feet, ankles, knees, and belly. Semi-starvation can cause edema Excessive alcohol intake can cause edema When you have prolonged excessive water intake. It can dilute the electrolytes in your blood and cause a low sodium in the blood.
Excessive urination can flush out electrolytes, minerals, etc.
Symptoms of fluid overload include a gradual mental dulling, drowsiness, weakness, confusion, coma, convulsions and death. When you repeatedly take laxatives, diuretics or vomit, your body will adapt to being constantly dehydrated by learning to retain more fluid than usual. When you stop these behaviors and start to take a normal diet, your body may continue to retain fluids until it learns that adequate fluid will be available, then it will release the extra fluid. People who abuse laxatives or vomit regularly are at the greatest risk for alternating between dehydration and edema. It may take from 2 to 6 weeks following long term dehydration for your body to get used to being normally hydrated again and flush out the extra fluid it has been retaining.