It's very likely it's a combination of both. When I had the seminar where my hospital trains people about the three surgical weight loss options, they talked about how grehlin rests in the bottom of the stomach and how it impacts people post-surgery (which is to say that sometimes I have to be reminded to eat because I just don't feel hunger anymore). Anyway, their studies showed that what determines the level of hunger your body feels (how much grehlin you produce) seems to be genetic. Surgery impacts that, especially with gastric sleeve since the lower portion of your stomach where grehlin stays is gone.

Food addiction is a real thing, however, and can't be dismissed. Habit is a STRONG motivator for most people, and reaching for food as an emotional response can be just as difficult to shake as alcohol or drugs.

Just my two cents, anyway. I'm not a clinician, so grain of salt and all.