Change is a process. In the beginning we are just as happy as a pig in mud, living life. We are just ignorant of any need of change, although we may be aware of the occasional difficulty or desire, but these are mild. Life goes on. This is the pre-contemplation stage.
The next stage is contemplation stage, where we might think we should lose a bit of weight. We have no idea how, but we might develop a bit of motivation to do something.
Preparation is where the work starts, as we examine the situation, perhaps make a decision to do something, and start exploring the possibilities, causes, drives of say overeating. There is much not being said about the problem. At this point in my development, I will say that there is no consensus beyond eat less and move more. Eating less is more important, but it is essential to eat well, take a few vitamins and minerals, water, and the like. There are five groups of causes of overeating, poor diet resulting from poor or wrong food knowledge including delusions, physical issues that drive appetite, environmental issues including life style, maladaptive behaviors including eating disorders, and food addiction. Each is an area of study to it's self.
Then there come action, where we test each concept on ourselves, and examine each concept for truth and validity. Some concepts do not work for us at this time, but may later have major impacts. This where we learn that this is and will be an ongoing battle for the remainder of our lives. Fortitude is required, now and in the future. Programs like OA, FA, FAA can help for those inclined. Philosophy, the art of reason can help others. Integrity, honesty with ourselves, commitment, and understanding of ourselves is critical.
Once we have gotten to where we want to be comes an ongoing maintenance, which does not mean going back to the old ways, but sticking to the new way. This is the most difficult of processes, and where "our diet" often lose toleration by others. The objective is not to overeat, and wonderful tasting and beautiful presentation do not make this easy.
Many of us spend our time yo-yo ing around in the last three stages, never at rest, never out of the problem completely. But then what do I know?