The biggest issue is that many people who do this diet to lower their fasting glucose possibly are unaware that in some people, their A1C will start to go up. Need to monitor your labs --a1C relfects approx. 2-3 months of what the blood sugar is doing; fasting is a snapshot of that morning. As for weight loss, the body will initially rid itself of water with the keto diet, but long term, the weight loss will stabilize and introducing carbs will allow the body to retain water...reflects the scale not your actually body mass.
Thoreau said, 'A man is rich in proportion to the things he can leave alone.'
I'm not pro or con Keto. A proper Keto diet requires a strict adherence to fat, protein, and carb allowances. In addition to being a treatment for epilepsy, it is being used with cancer patients and with people who have memory issues and those with a family history of memory issues. My doctor advises her patients who want to try it to work with a nutritionist. My limited experience with it was with one of my personal chef clients with cancer who was on a Keto diet. It's not as simple as a lot of people make it out to be.