Two types of mental processes that we use to govern ourselves are conscious regulation, of which we are aware, and non-conscious regulation, of which we are not aware.
Conscious, willful regulation of our own behavior takes effort and depends on mental energy resources that can get easily depleted. This kind of self regulation is short-lived. We can only go so far on willpower alone.
Non-conscious mental processes are automatic, by comparison, and they do not require an unusual expenditure of effort. They are fast acting, long-lived, and can occur repeatedly without us feeling mentally depleted.
Overeating, binging, and being overweight over a lengthy period of time have come to be governed by non-conscious, automatic mental processes. These mental processes are very hard for us to change because they happen and happen and happen before we know it.
Then we go through the arduous, bumpy, oh-so-very conscious struggle of changing ourselves. We do what it takes, and it takes all our effort often, to go from being overweight to losing weight, to maintaining our weight loss. We expend lots of mental energy, use lots of willpower, sometimes to no avail. These are no match for the well stamped-in, non-conscious, automatic old patterns that we're trying to change.
Once we cross this treacherous chasm of change and remain at our ideal body weight for a long enough period of time, we are now governed once again by automatic, non-conscious mental processes. Only this time, these processes are in the service of weight management rather than weight gain.