So much of our adult behaviour is brooding from our childhood, and I can completely identify with what you have all been saying.
For me, I think a lot of my eating habits have been passed on to me from my mum. She's one of 7 children so food was never freely available when she was a kid, so she took her sweet time eating her food, she was always last to get down from the table. And, in the same way as you have already said, it was the whole "finish what's on your plate" thing, as she saw how much her mum and dad worked to provide for the family. So she would eat even if she didn't want to. Then when she started working and was still living with mum and dad, she had the freedom to start buying her own treats and being able to afford extras, and the weight started piling on. The same thing happened to all her brothers and sisters, apart from 1 who has always managed to stay slim, which has lead her to think she's somehow 'better' than her siblings (but that's a different story lol)
Then while I was growing up, mum battled depression and turned to food a lot for comfort, so I guess I'm following suit, minus the depression.
I love my mum more than anything but sometimes I wish she would have set a better example, but now I'm a fully fledged adult myself I can't put the blame on her, that's if 'blame' is even the right word. Some people turn to drugs or alcohol to cope, she turned to food, and - like drugs and alcohol - it's become an addiction for her which she's managed to quit many times but still struggles.
I entirely believe food can become an addiction, but losing weight doesn't get the same recognition as quitting smoking or drugs or drinking, surely it can be just as overpowering and destructive?