A mixture of things.
Food deprivation as a kid (abuse) and young adult (poverty) - eat what you can, as fast as you can, as it'll be taken away from you or you don't know when you'll get to eat again. It could taste like shit (and frequently did), but what was important was to get it down you as quickly as possible.
A violent relationship. If I was too heavy for him to pick up by the throat, I was less likely to experience being choked out again. Even being bounced off the walls hurt less with a good layer of fat to cushion the ribs and legs. It made the prospect of dieting to get lighter distinctly unappealing.
Prescription of Depo Provera - apparently, it was absolutely NOT going to result in weight gain, if anything, it would result in weight loss, according to the prescriber who was coincidentally being given targets for long term contraception takeup. Three stone in 4 months, that did. Result in terms of the previous category, but not great for the BMI.
Autoimmune Disease. Pain, tiredness, dizziness, migraines. Anything that was quick and accessible would do. Especially when the strains of travelling to work and working were such that a two mile walk at lunchtime to the nearest shop selling anything other than chocolate or crisps was impossible to fit in at lunchtime.
Leading on from this, working for the NHS. At the time, all the franchises selling food on site were Burger King, a place selling massive baguettes or cake, a newsagent selling chocolate and crisps or Costa. The surrounding shops were sweet shops and I was too tired and sore to think about shopping, planning and making packed lunches, especially as there wasn't anywhere onsite I could eat them, as the contracts for the franchises stated that only people eating their food could sit in the sole area with tables and eating in your office was banned. These days, as M&S seem to have taken over everything, I think it would be much, much easier to get hold of a nice salad or sushi.
My ideal would be to work next door to a Pret or Itsu. I now work next door to a Londis. So I don't go in.
I just don't like the smell, taste or texture of packed lunches. Even things I normally love turn revolting once they've been in there for six hours, refrigerated or not - and, as again, I'm down to desperately trying to grab a few seconds to shove something in before I'm spotted eating at my desk (not allowed), it needs to be portable, not messy, zero smell and certainly not anything like leftovers to be reheated and consumed at my leisure.
I think I'll start losing some weight again now I'm back at work. But whilst I know exactly what would work for me - access to fresh ingredients, salads, etc, with lots of choices and time to sit somewhere peacefully and eat them slowly - it's not something available to me.
Oh, and gyms need to reopen properly. The local authority ones are still closed and the private ones are giving you 30 minutes in the pool maximum with you having to book days in advance, or one hour from coming in the door to leaving it again, which isn't worth the monthly fee. I need access to safe exercising, thanks to the autoimmune condition - a jog or walk would damage joints and tendons so much that I'd be unable to stand up for about 9 months (been there, done it, have plenty of injuries from silly things, thanks to the bolloxed musculoskeletal system).
And I'm tired. So fucking tired. There's no physio available, my treatment plan hasn't been looked at for months, I'm in pain 24/7 and I haven't got the mental or physical energy to do more than drag myself to and from work. So whatever is put in front of me for dinner, I'll eat it.