Sir Peter Gluckman chalks it down to the body's biological "set point" in his book Fat, Fate and Disease. But most people tend to assume the subject has fallen off the wagon, and reverted to their old habits due to a lack of self-control.
I've no problem with anyone who wants to try to lose a radical amount of weight. It is actually a marvellous feeling. I still remember the sense of satisfaction I had after crossing the finish line in the 2007 Kepler Challenge - it took me seven hours 55 minutes to run, climb and walk that particular 60km; there is no way I could have done that when I weighed 135kg. And to be fair it was still a massive test at 88kg.
I now train regularly at a a martial arts gym, mainly in muay thai. I have conversations there and in other places with people who have lost weight, or are trying to lose weight. I love to hear their stories and see them challenge themselves and others.
But am I inspired by stories of radical weight loss? That answer is actually pretty complex. I am inspired, but I am also haunted.
What haunts me is the elephant in the room (excuse the pun) - that is the identity destruction that comes with such a radical change in form. People who have been the same approximate size for their whole lives simply do not understand what it means for your body to undergo such a radical shift - they just assume that the subject who has lost weight must have hated their old form and must now be satisfied with the "better" one. This, sadly, is not so.
What is more accurate is to understand that a range of body sizes exist in the psyche of these people - I call them multiple authenticities. I have a minimum of three I think - an authentic "fat Andy", an authentic "athlete Andrew" and an authentic "Dad bod Andy". Coming to terms with these and living with them all is a work in progress for me.
Our system provides virtually no psychological support for people who undergo radical weight loss.
Mostly it is just a smack on the back and a "good on ya mate". This can result in a range of problems, from injury through over-exercise to eating disorders.
I think the most difficult part of radical weight loss is how someone learns to live with their multiple authenticities in the aftermath. This includes coming to terms with the (almost inevitable) weight regain, partial or otherwise.
Philosopher Rosie Braidotti talks about the "embrainment of the body" - how the body remembers and "thinks" and acts on itself. For me this accounts for Sir Peter's body weight set-point.
Our mind is not in control, but our society assumes that it is, and that comes through in the way we treat ourselves. For instance, I used to joke about running away from "fat Andy". I rejected his body in favour of the "better" athletic Andrew. But, in doing so, I lost a lot of upper body strength, something "fat Andy" had a reputation for. "Dad body Andy" has some good strength, but I can't run 10 km in 41 minutes any more, it's more like 47 minutes. Sometimes I feel like a failure because of this: "athlete Andrew" has lost his speed.
Counselling and/or psychotherapy are needed as much as physical work in the aftermath of radical weight loss. This allows a person to talk freely about their body and life, without judgment, and to come to terms with what weight and weight loss symbolises for them.
