My perspective is very skewed from having gone to an all girls school where anything other than really thin was unacceptable. At about 13, anyone who was not very skinny felt pressure to diet. We were not overweight or even anywhere near the upper end of healthy bmi range, but we weren't thin enough.
I went on an 800 kcal a day diet as did many of my friends (again, we were all middle or lower part of healthy bmi range). We would pass in the corridors between lessons and say, 'what are you on? I'm on 300, you've only had 80? I am so jealous'. I couldn't join in family meals anymore and starting microwaving horrible weight watchers ready meals.
If I weighed over nine stone, that was it, above the knee skirts were out until I could get down again...the shame!
If you were very thin you could have an emotional crisis and it would be dramatic, mysterious, intriguing. If you were not thin then your emotional crisis was an unattractive embarrassment.
Our attitude to food became very distorted. I remember a party where my friend had made lots of cakes and puddings, no one ate much and then when it was just the two of us left we were like 'thank god they've all gone, now we can binge the rest'. If I bought something to eat while out shopping, I would eat in it the toilet as I was too ashamed to be seen eating, it thought people would think I should,not be eating at my (totally normal) size.
Anyway, guess what, we have all developed a starve/binge mentality and many of us spent years yoyo dieting, all as a result of actions taken when we thin anyway. So depressing. For those of us who have suffered trauma yes, food was in prime position to become about comfort or control.
Also when very depressed people rarely feel up to cooking healthy, sustaining food. Or often literally use the sugar hit from a bar of chocolate to give them the lift they need to get up and go to the loo, to shower etc.
If people have not got a long term unhealthy relationship with food, or have not relied on it to self medicate (massively viscious self sabotaging cycle of course), they are just not going to understand.