I think you also need to look at both sides of the story
We have the OP who admits she has an unhealthy relationship around food
We have stories to show how controlling her parents still are, for sharing a bag of crisps and. for making a bar of chocolate last. How mother would say two cakes were more then enough when granny was dishing them out, which we all know is really sensible eating
We also hear that she allows her own child to graze all day
Im a child of the 60's/70's. It was three meals a day - eat or go hungry. We had no snacks. Sweets were rationed, a mars bar between the three of us girls, biscuits on a Sunday , a rare packet of crisps., we often went to bed hungry , right through till the 80's ( recessions and mass unemployment saw to that ) All kids were skinny, well working class kids were
I also like the OP got into junk food in a huge way once I had left home and had my own money and like the OP, piled the weight on. Take aways had sprung up on every corner , food was cheap, it was easier to get a take out then go home and cook for one. Only once the clothes stopped fitting, I soon learned to reign it back
Im hitting 60 now. Ive been on 3 diets in my life , Ive mostly kept to a Healthy BMI, the last pile on was due to severe depression, which I came out of last year and Im back on track with self care and healthy eating, Healthy BMI and a varied diet. I do share a packet of crisps and I do eat chocolate a square at a time and honestly, I couldn't eat more then one cake
Now I can sit here and blame my parents for all my troubles , and I admit I have done in the past, but I finally did grow up and realise I was an adult and I was the one in control. I control what I eat as in I dont go to bed hungry anymore because I cook healthy filling meals which I like and know I will eat. I dont eat cake and biscuits after dinner cos Im not hungry because my evening meal has been enough. .I dont eat crisps every day - and I love crisps, I dont eat chips and fried food very often and takeaways seriously are a rare treat - think once every six weeks or longer. Yep I back to those 3 meals a day and no snacking :)
Parents live with me now but when they were on their own, I would never ever ever have thought of helping myself to their food when visiting I would never do it in my sisters houses either so I dont think thats really abnormal or weird