Absolutely agree, that discipline is a key factor in weight maintenance. Until I turned 38, I could eat just about what I wanted to eat, and never gain more than two pounds. Nearing 51, that has changed a great deal, at least for me. Now, I must accept the fact that if I'm going to stay slim, I cannot eat as much as I may want to eat, nor as often as I may want to eat. Nor, can I eat the THINGS, that I want to eat. All this, and exercise, too.
Recently I attended a 'welcome home,' party for friends who are moving back, from Florida. The average age at this gathering, was around 60. My sister, sho is 54 and weighs 108 pounds, and I were among the vast minority of slender people, there. Not just that: these people were more than fifty pounds, overweight. What were they doing, during the party?? Eating. And, all the wrong things. As for exercise, when you're that heavy, it's much more difficult to work out.
When I was young, I used to think that movie stars, just 'looked that way.' Now, of course, I know how hard it was for them, to stay thin . . . especially since cameras, add weight from all angles. I think that's partly why so many of them, smoked themselves to death.