&quot;Though I drank tons of water during Soylent, according to the instructions, those missing 4 lbs of water weight indicate I may have been less hydrated when I came in the second time.&quot;<p>More likely: you carried a lot less liver and muscle glycogen by the end (a typical result of low carb intake), and glycogen binds a lot of water.<p>When I first keto dieted, I lost <i>13 pounds</i> in the first 2.5 days, probably almost all water, much of that probably from shedding glycogen.