Well a lb equals about 3500 calories. So if you pass your "maintenace" daily calories (or the amount of calories needed in order for your weight not to fluctuate) by 3500, then you will gain a pound. I doubt you ate that much in 5 days to gain 6lbs of fat! So therefore I say most of it IS water Now, just drink a ton of water, reduce your salt and carb in take and you should see your weight sliding down a bit..