Over a 3 day hypocaloric phase (sub-maintainence cals) i could lose 2-5 lbs (most of which is water).......then after the refeed/overfeed day, i'd gain most of it back (usually 75% of the weight i had lost)....but this was a GOOD thing.....overall weight loss was about 1 lb. a week (net, after the refeeds/overfeeds), and most of it was bodyfat, not lean mass or water.....
I think everyone should buy calipers....the scale is just not a good indicator of it you are gaining or losing fat....for example, in the past 7 weeks i've put on 8 pounds, but my caliper measurements have not increased, so I know the weight I gained was mostly water, with some lean mass and probably very little bodyfat (which is likely visceral fat since I have no increase in skin fold measurements)....