Wouldn't it? Do you really think that someone with no chemical dependency giving up a substance is as simple as someone with a chemical dependency giving up that substance?
Simple? Yes. Easy? No. And probably the method and mechanism in the second case (chemical dependency) will be different from those in the first case.
By 'simple' I mean that the method and mechanism is well known, scrutable to a reasonable adult without any special effort of mentation, and not requiring complex calculations, caveats, hidden factors, or other complications. Cold turkey is simple, but gradual weaning is also simple. But they are not easy.
I would have thought that that was a perfect example of it being more complicated than a simple matter of willpower.
I am, and always have been throughout this thread, making a distinction between simplicity of methods and mechanisms, and simplicity of motivation.
My thesis is that while weight-loss motivation is a complicated thing, the methods and mechanisms of weight loss are relatively simple: Eat less, exercise more. I am in disagreement with those who argue that the mechanisms and methods of weight loss themselves are complicated, or that a motivated person cannot make progress by implementing the two simple principles in their daily life.
If you are saying that the methods and mechanisms of weight loss are simple (but not necessarily easy), and that the problem of weight loss motivation is complex, then you and I are in perfect agreement.
I have no problem with your characterization of it being "a simple matter of willpower". Simple but not easy. And willpower itself is a complicated thing. So. The methods and mechanisms are simple. Identifying the real problem as being one of willpower is simple enough. Solving the problem of willpower is where the complexity arises.
But I am essentially arguing against the idea that we should tell people who
have solved the problem of willpower, or who
are trying to solve the problem of willpower, that they should not bother eating less and exercising more on account of how the methods and mechanisms of weight loss are too complicated for their motivation to make a difference in such a simple way.
Then there's potential psychological issues.
Which I have explicitly and repeatedly decoupled from my discussion of the complexity of methods and mechanisms.
Would you claim that overcoming anorexia was as simple as eating more?
No, but I would say that overcoming an underweight condition due to anorexia was as simple as eating more. Possibly as complicated as ramping up food intake over time, and perhaps choosing specific kinds of food during the early phases. That's method and mechanism.
The psychological issue of anorexia itself, is motivation.
I'm imagining a rather absurd conversation:
"My anorexia is cured. I'm once again motivated to eat. Can I get back up to a healthy weight by eating more?"
"No, weight management is more complicated than that. Don't bother trying to change your weight by changing your diet. It doesn't work that way."