Both of your scenarios assume that the issue is due to some fixable personal failing, and both of those assumptions are unfounded. “Lack of planning” is how you might describe “poor executive functioning” if you were to attach a moral weight to it; in reality, poor executive functioning is itself often a symptom of trauma, particularly complex or developmental trauma. It is also a feature of autism, particularly in how it manifests differently among women. Similarly, there are many people for whom no known weight loss method has worked without intolerable costs. (Suicidal ideation, dramatic hair loss, debilitating fatigue or cognitive deficits.) This seems to be one of those things that people often refuse to believe, instead gas lighting the hell out of the people who suffer from this. I have known people who’s compulsive behavior absolutely contributed to their weight problems (and in those cases, trauma was also a factor), but I’ve also known people who have done and tried everything, and the way they suffer is not something I would wish on anyone. We don’t yet fully understand how trauma, particularly long term trauma, affects the body, let alone the metabolism, nervous system, endocrine system, or even GI tract, but everything we are learning seems to point to profound effects. It seems incredible to assume that there might not be purely physiological mechanisms at work beyond the control of self-directed behavior.

In general, trauma symptoms encompass many more dysfunctional behaviors than is often understood by lay people, and while self-destructive behaviors in response to trauma or persistent C/PTSD are no less self-destructive because of their origins, describing them in moralist terms is actively harmful. It is often more accurate, and compassionate, to describe those behaviors as adaptations to stress that have become maladaptive. They are not moral failings; they are the result of bad conditioning. Put another way: if the only tools you have for internal regulation are shitty tools, you learn to depend on shitty tools to survive.

This does not make traumatized people any easier to be around or to help. You still need to draw your own boundaries, as you noted. But if you’re able to approach such people within your own acceptable boundaries with an open mind, and the willingness to point them towards trauma treatment that might actually be helpful, those conversations you’re not sure how to have might have better outcomes.

For further reading on trauma I’d recommend Van der Kolk, Levine, and others.