No changes in willpower will almost assuredly come with gaining all of that weight back when whoever falls off of whatever "wagon" theyre attached to. I did your diet years ago, and it works. But I gained it back when I got sick of the diet and didnt want to do it anymore. GLP shots have the same pitfall along with procedures and similar "shortcuts".
The only way I've kept off my weight for the last handful of years without any bounce back is directly related to my portion control, planning, and at least knowing "roughly" what amount of calories Im eating when I go out. There isnt a single occasion where I dont eat something absolutely delicious and cry out like a little bitch inside my head that I cant have anymore. There are still nights where I fall asleep looking forward to breakfast.
Also, not to knock that diet in particular - a person on a Carnivore, Keto, or similar diet rarely notices that they smell like "used oil" to people around them. Its not from aging, or lack of cleanliness. It is directly related to the diet.