Well subcutaneous adipose tissue can actually store a shitload of water, about 1:3 ratio.  So A person with 300lbs of subcutaneous body fat (a 500+ pounder) has the chemical capacity to retain up to 100lbs of water weight (at the extreme).  Gross.  (this is why super fats go on a diet and crash 50 or 80 lbs in a couple weeks, mostly from getting sodium and fluids into more reasonable numbers.)  Don't make em less fat tho lol