Thanks! This plays nicely with my confirmation bias; I've been on a ketogenic diet since March and I've felt much better because of it.
I would certainly worry about 20 lbs gain, carbs or no carbs.
After switching to keto, glycogen is used up gradually, due to no carbs entering the body. And the water is also lost. Therefore, the "signing bonus" of the keto diet - a significant weight loss in the beginning, but due to water lost, not fat burned.
BUT. That only accounts for about 4 kilos, maybe just a bit more. You can't really blame water for a gain of 20 pounds.
Am I missing something?