I managed to give myself food poisoning on Friday night. 12 hours of vomiting, 24 hours of tossing & turning, then 48 hours of dehydrated stumbling around. It hasn't been pleasant. I've "lost" 6 pounds, but that's all digestive mass.
Effectively, it's been a near-total fast for 96 hours. Everything I ate on Friday came back up, I had nothing at all on Saturday, and all I had on Sunday and Monday was a pint of ice cream, a candy bar, three slices of bacon, a couple eggs -- and a ton of sugar water (mostly sports drinks).
I've felt somewhat dehydrated, but I think that's been helped by burning off whatever glycogen stores I had -- and burning up those stores frees the associated water. This 'free' water is much of the weight lost when you first go low-carb; burning off glycogen stores doesn't also burn fat or break down muscle tissue.
Burning glycogen stores should make your lean tissues look more lean, too, by getting rid of the padding that comes from the water. The other major way to do that is to continue burning off fat -- just like high-grade cuts of meat, humans have fat tissue streaking through their muscles. Burn off that fat, and your arms and legs will look tighter, less 'puffy.'
I've felt some clarity of thought in the last few days, too. I haven't been low-carb however; those sports drinks have been high in sugar. Yet I think I've mostly burned that sugar off; at least, it's prevented me from burning off fat stores. But I've stayed away from grain and veggie oils the whole time, and I think that's helped.
Overall it's provided me an incentive to clean up my diet still further: (1) give up those corn chips, which primarily come with queso, which (when I can't explicitly check) is most likely some kind of veggie oil omega-6 goop instead of real cheese. (2) Stop with the potatoes. It's one of my major weaknesses now, and probably will continue to be, but I can start by not getting fries when I do get a burger (wrapped in iceburg lettuce instead of a bun, of course).
Down 26 pounds from my max... heh. My apartment complex is doing its own "Biggest Loser"-type thing starting tonight, and I'll be starting that off after five days of unintentional fasting. Wish me luck!