This is true. Broadly speaking the physics don't differ between people.
Though, there are people like myself who can't really gain weight even if we try. lucky problem i know. I don't have any special willpower other folks lack, and really, if we're honest, I probably have less willpower than most people.
The thing people often overlook is that my inability to gain weight is no different than other people's inability to lose it. The physics are the same, if I ate more, I would gain weight, my body is not special in that regard, whereas if others ate less, they would lose weight, their body's are similarly not special in that regard. But the hormonal balances in our bodies that tell us to eat more or less after given inputs are inherently different and we largely have little control over how that dice roll lands in our genetics. Neither one of us can fight those signals any better than the other. My body tells me to stop eating so I stop when another dudes body screams at him to keep eating. To do the opposite is fighting hormonal signals telling our brains to tell our bodies to do what it thinks our bodies should be doing, overpowering that is not easy. My body forces me in one direction and theirs another.
I just hope more people realize that many folks inability to lose weight is not a result of their lack of willpower.
I'm largely agnostic on the drugs. Proper use of medicine is life changing and I want people to leverage everything they can to live fulfilling lives.
But I do fear that because history shows us in the world of bodily health that easy buttons often come with consequences, we may be getting a little loosey goosey with the access to these things. I hope not. But it is certainly the open ended question nobody can definitely say here with the GLP-1s.