By the end of week 4, I seemed to have natural appetite suppression and a conscious control over how I chose to respond to hunger signals. That is one of the first stages. I might still have had a feeling of tiredness or fatigue if I didn’t eat for a while (such as my first 30-hour fast*, which was at the end of week 4), but I could actually DO the fast.
[*Note: fasting is not necessary, but it was out of convenience - I had breakfast one day but didn’t have time for lunch and worked late, so I decided to skip dinner and just go to bed, and then when I got up the next day I discovered I could keep going until lunch time. I was like a kid playing with his newly discovered superpower.]
Probably by weeks 8 - 10 or so when I started to feel like I had normal energy levels all of the time regardless of when, how much, or what type of food I had eaten, and could easily skip meals for convenience and go for 24 hours between meals if I wanted to without it taking much effort.
It’s a continuous process. I’m in week 21 now and getting close to what I assume is being fully fat adapted. It’s weird, really, the sensation, when you take time to stop and notice it, of having total conscious control over your eating behavior.
There is a paradox of weight management which says “Why would a fat person ever be hungry?” because since he/she has enough stored energy, why would they feel a need to eat more? Why doesn’t the presence of body fat turn off the hunger signals?
When you are fat adapted, the paradox is resolved. You have created the metabolic changes needed to easily burn stored (or eaten) fat, so your body just dips into those reserves without complaint, whenever it needs the energy. It no longer has the “Oh crap, I’m starving, make the brain find me food” response.
I really am almost never really HUNGRY any more. That makes me able to use food as a tool for health management rather than a substance that I crave or am compelled to eat. Meaning I choose when to eat, what to eat, based on healthy food choices, proper amounts, and what fits with my schedule.
When you get to where you can do that naturally, without a feeling of being deprived, hungry, or fatigued, that’s probably where full fat adaptation would come in.