I believe that ketosis was meant to be our primary metabolic system for fueling our bodies. We tend to think of ketosis as some sort of backup metabolism in the modern world and sugar and carb burning as the more normal way of eating. The advent of the carb heavy diet was also the beginnings of modern diseases under the umbrella of metabolic syndrome. Most of the metabolic issues that made you unhealthy the first time around were related to elevated insulin and running on carbs/sugar as your primary fuel, which is meant to be the back up system, and prolonged living like that leads to metabolic syndrome.
So what happens when you get out of ketosis is you start heading back again where you just left. I don’t believe it’s possible to switch back to a carb dominant diet and be healthy too. You might be able to stay in ketosis at a higher carb level after longer fat adaptation.
Your weight loss is the result of reversing metabolic damages and getting back to what was the intended primary way of eating for humans. “Healthy whole grains” is a myth. And starchy root vegetables just fatten you up. That’s why I’m here to stay.