The point is that you can't necessarily will yourself to eat less or not have sex or stop wasting time, either. It looks as if you can, but appearances can be misleading.
Do you think you can necessarily will yourself to drink less (alcohol)?
The debate about "personal responsibility" vs "can't help him/herself" is very old.
No. More precisely: I'm pretty sure I can. I'm pretty sure most alcoholics can't. But they may be able to will themselves to drink no alcohol at all, just as it may be easier to follow a diet like "nothing containing sugar" than one like "no more than 2000 kcal/day".)
I suggest that we should actually care less about whether in some abstract sense we can do these things (exactly what we "can" do will probably depend strongly on the definition of "can"), and more about whether we will. And on that, I think the empirical evidence is pretty good: for many people, just deciding to eat less will probably not result in actually losing weight and keeping it off.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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