if you eat keto, your glykogen storages get empty and you will loose a lot of water as well. dont worry, this is primarily no fat!
but because ive read about keto also in another thread a few seconds i ago and i still dont understand why people still do keto, i will post here the same. im really interested in the reasons why you are doing that.
why are you eating keto? if you love to eat fats and if you its easier for you to eat less carbs than less fat, okay, then go for it. but thats it. keto is not beneficial for us as bodybuilders, for someone that wants to keep his intensity during training as good as possible to keep those gains during a cut. you wont loose more fat with keto nor will you have a better performance in the gym (in regard of performance even the opposite is probably the case). i know that many guys, especially some old-schoolers recommend keto but if you check the research, it clearly sees no benefit but a few possible negatives about it.
but regardless which diet - adherence is key. without adherence you can have the best meal plan, you still wont reach for goals.