There was some weird things in my childhood. My weight gain actually started from my sister secretly over feeding me at the same time that she took food, just so if she got caught, we would both be told off. I was only about 5 at this point. It didn't take long for me to end up bigger than her but when I was, she used it all the time against me (you're bigger than me but younger) and I can never understand the mindset of my sister with that, but she was just a young child herself, even if a few years older and actually dealt with bulimia in her older years, so I think our childhood definitely did something to trigger eating issues.
Because I was then bigger than my sister, I had a lot of "no, you can't have that, but your sister can" type comments from my parents and it resulted in me just secret eating and stealing money to buy stuff from shops and eat it by myself. My sister would then set up her phone to record me secret eating in the night and I remember them all laughing about it with it playing on the living room TV... I think things like that made it worse.
I was about 15 stone when I left secondary school and gained 4 stone in about 6 months after leaving. I then stayed around that weight, fluctuating a couple stone, until I moved out at 20 and gained a further 8 or so stone, just by eating whatever I want, knowing I didn't have to do it secretly, etc. and definitely just binging and enjoying food with there being no bad feelings around it.
I'm not trying to blame my weight gain on anything but me eating way too much, but I don't doubt there were factors that made it worse for sure!