I attempted a 7 day water fast to detox and made it only 5 days because my back pain was just too intense. And I have had three children so I know intense pain when I feel it. Well I eased into eating as recommended, slowly with organic berry juice and then Greek yogurt the next day etc.. I didn't eat solids until the 4th day. But now I have a case of edema in my legs (mainly right),heavy bloating of my body and face, and a swollen thyroid.
A little history:
I do get heat edema, or edema if I sit or stand a long time, but never when IFing.
I normally just IF no longer than 36 hours. I normally do not eat fruit or yogurt.
I chose to fast this way because many cancer survivors recommend it.
I am not sure if this would apply to your situation as this is normally seen in anorexics or people who have been starved for prolonged periods of time - but this sounds like "refeeding syndrome". The edema is a common sign of this.
I too get the heat edema, but recently I've been adding 1/8 tsp of baking soda and 1/4 tsp of a potassium based salt substitute (MOrton's) to my 32 oz water bottle and that has helped tremendously. My fingers look like fingers and not sausages.
So, if you are experiencing a bit of a refeeding phenomena (refeeding causes a dip in electrolytes) coupled with the heat induced edema, you may benefit from adding the electrolytes to your drinks.
I can't speak to the thyroid, but low thyroid can cause edema as well.
I have do fasting for up to 14 days for Spiritual reasons. I have not experienced edema. Our Shaman makes sure we drink a special 'tea' (its not made from tea) and I know it has some salt in it, as keeping electrolytes in balance is key when fasting.