OK, you have a point so I will tell the secret....the will power came from a source that is unavailable to most cases. You see one of the side effects of my severely misbalanced gut was that enormous amount of particular type of bug had taken over half of the living space. The buggers then found their way into my bladder and from there you know where it goes. So I was suffering from chronic bladder/urethra infection that was unbeatable by any means until it was realized where the source of the problem is.
So, apart from being fat and underpowered I was also having serious trouble with sex [it would simply hurt rather than being a pleasure]. Now for a guy in his late thirties this is one HELL of a motivation! So when the doctor said 'I will make it so that this chronic infection will go away IF YOU EAT what I tell you and you do it seriously" I was like "I'll do anything to be fully functional male again
On the other hand of the spectrum one of my nieces, age 11 who ran into the obesity issue years ago. Being a child she has less of a discipline, willpower and motivation. On top of that in venerable mind as hers [and that of every girl and also boy of this age] the desire to get slimmer turns counterproductive especially if bullying occurs both at school and outside. The girl tries so hard but struggling with the bugs and struggling with society and your own mind proves extremely difficult.
Thus i do not consider my story a showcase for willpower - maybe I don't give myself enough credit but there it is....
I have written many