The initial symptom was wanting to eat all of the time, even if I wasn't hungry. My brain was convinced that I had to spend huge chunks of my time chewing on something flavorful.
So I sliced off some very flavorful cheese and nibbled little tiny pieces during the morning. That seemed to work. Note that I avoided all artificial sweeteners. There's some danger there that I felt I should avoid.
Eating a bunch of cheese leads to constipation. Some fiber every morning fixed that.
There were a few other things. My energy level dropped right off, then came back. Now I have much more energy than when I started. I had a little bit of brain fog, but it was manageable.
The biggest thing I've found about keto is that my personality changes. I am much more relaxed and sedate than I used to be -- more on an even keel. That's not necessarily a benefit. It was just unexpected.
ADD: The crazy thing about keto, as opposed to just IF, is that you have to be really OCD about what you eat. Manufacturers sneak carbs into everything. A food journal was critical for me -- and it was something I felt I didn't have to do, since I already knew so much about nutrition! Good thing my SO talked me into doing one.