This came up in the Low Carb Leader (LCL) podcast with respect to an athlete trying to get “cut” after periods of unsuccessful dieting, and the the basic response was to go into a “building phase”.
For us non-athletes, that mostly means eating to heal your metabolism and stabilize hormones first since those are ultimately what control the storage of body fat.
This is why we advise against restricting calories because so many people have been dieting for so long, the chances are that they’ve already reduced their BMR and the focus should be on restoring it.
After a period of time that will vary from person to person, but I’d roughly say from 4 to 12 weeks, the focus should be on eating keto with plenty of fats, even if that means gaining some weight initially.
Before fasting, the idea of eating more to increase BMR and gaining weight until you’re body is really ready to lose weight would be very frustrating, but with fasting you can do both and this is even addressed in the LCL podcast where there’s a cycle of feasting to stimulate BMR followed by fasting where the body consumes the body fat.
This feasting/fasting/feasting cycle is what I’ve come to find is working better for my body and is raising my BMR in the process as evidenced by eating more and still not gaining weight over the long term.
After someone is definitely fat-adapted, they are probably ready to slowly reduce dietary fat and let the body release it from adipose tissue, thereby losing weight - this effect is predominantly from the reduction of insulin, but also the upregulation of what’s need to release and burn fatty acids for energy.