My observation is that the fat people who become "normal" size and maintain that size for more than just a few years, manage to do this through doing the hard work it takes to continually and consistently oppose the natural physiological desires of their "reduced obese" bodies.

Rather than allow their bodies to tell them how to eat, they use their minds to overrule those bodies and consciously choose to eat food containing far less calories than their individual body desires.  Forever … one-day-at-a-time. 
It is possible, but it isn't easy.  
See Running Down the Up Escalator.

First, let me clarify that my definition of a "fat" or "obese" or "reduced obese" person is not someone who merely hangs somewhere around their BMI Obesity border. Meeting that criteria requires a person to put in more than two or three years at a weight of … at least …. 20 to 50 pounds above their BMI Obesity border. To me, those who fail to meet that requirement are merely "overweight", a condition that is often temporary for them. Although many of these people term themselves as "fat" or previously obese, in general, they appear to have a very limited understanding of true obesity or the fat condition.

An overweight person tends to think that because they went on their first diet and easily lost and kept off 10 or 20 lbs, then an obese person, on their 50th diet can do the same thing for a longer time and lose and keep off 100+ lbs. This attitude is easily seen within the numerous online diet forums that are full of overweight or formerly overweight people who are eager to offer copious advice and personal judgments along these lines to people who are obese or reduced obese.
This unequal comparison … apples to oranges … often confuses people who are truly obese or "reduced" obese and frequently results in negative self-judgments which are just wrong.

So, applying this clarification, There are psychological desires (of the mind), and physiological desires (of the body). What does it take to continually and consistently use one's mind to oppose the natural physiological desires of one's body? Is the ongoing difficulty of opposing those desires worth the effort that it takes to be "normal" weight?

This is a Judgment call that depends   
on the severity of the individual's mental pain which is caused by the culture's fat-bias, and the severity of the individual's physical pain which is caused by denying to one's own obese, or reduced obese body, the food substances which that body believes it needs for survival. 

We must each decide this for ourselves. Thus far, for me personally, the balance tilts toward accepting the physical pain to avoid the mental pain. However, my personal dieting ...

    

                                

I am definitely the best witness of my own experience. For a lifetime I’ve examined myself, my behaviors and how they affect my body. I’ve gathered evidence, researched the issues, analyzed the data, and formed conclusions about myself which are based on the relevant evidence.

I’ve chosen to view dieting as a hobby, and for many reasons, I plan to continue my personal involvement in that activity.

However, I’m thinking that it is time to end my relationship with Fat Sigma. While doing so, I’d like to make my reasons for the breakup clear. So, I’ll reverse the ususal breakup statement which is shown in the picture here, and say to the Fat-Biased-in-Society:

“It’s not ME, it’s YOU.”

The following article is one that I wish I had written myself.

They Don’t Know Fatties
          by Ragen Chastain  -  www. danceswithfat

I was thinking today about how often we are told that, as fat people, everyone who is not fat is a better witness to our experience than we are. How often someone is considered an expert in weight loss, or becoming thin, or being not fat simply because they happen to be thin.

We are told that we’re not competent witnesses to what and how much we do or should eat, or how much we do or should move. Our bodies are held up as proof that we must be lying or deluded and that we can’t possibly know, or be doing, what’s best for us. We are told that, because of how we look, we should be subject to more scrutiny than those who don't look like us, we should lose our right to speak for ourselves, we should be stereotyped and stigmatized and bullied and war should be waged against us - that the way we look means that we shouldn't get to choose how highly we prioritize our health or the path we choose to get there like everyone else does.

We are forced to listen to people like Jillian and Bob on The Biggest Loser prattle on insufferably about how fat people think and what fat people do and what it's like to be a fat person as if we are all walking around under the guide of the same brain just because we share a single physical characteristic. We, and the rest of society, are told that everyone from Dr. Phil to Dr. Oz to random people on the internet know more about how and why we think and act, and what it's like to be us, than we do.

When we tell people that constant social stigma is damaging to our health, we are told that it's for our own good and we should be grateful to hear that our bodies are socially unacceptable more often and more aggressively than we already are. When we tell people that we are not suffering from obesity,...

The following Poem expresses the pressure women feel
to take up less and less space,
to be quiet,
to be small
and to eat sparingly.

"Shrinking Women" by Lily Myers  

               We are not all the same.

I totally agree with the below quoted Facebook post by Kate of This is Not a Diet - its' your life. 

"When someone says they have come to peace with their body, whether it's loose skin, extra weight, cellulite, stretch marks or any other perceived "flaw", let them have their peace. If I say I'm happy with my weight, I don't want you to give me your ideas for weight loss solutions. If I say I am at peace with my cellulite I don't want you to tell me it can be removed with a magic cream. If I say I love my thick thighs, I don't want a list of exercises to slim them. And if a person says they have come to terms with their loose skin and see it as a reminder of all they have been through, not a flaw, they really don't need you to tell them to have surgery.

I think a lot of people get so wrapped up in their own body issues, they can't imagine how any person can really make peace with "flaws" such as these. They believe the person must be lying or fooling themselves. This is a false perception.

Making peace with your body isn't about having a flawless body, it's about how you feel in your mind. There are thin people who hate their bodies and fat people who love their bodies and every variation in between. Don't make the mistake of equating fixing your body with fixing your self-image. If surgery is something you personally want to do, that's your choice. But it's not everyone's choice. Let us enjoy our peace, in peace.