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I totally understand what happend to you, because in some way, it happened to me as well, and not because my family was poor, but because they weren't there most of the time, and I always had to improvise or find food, and when they were there, they were abusive.
Good thing is, by them not being there, I had the privacy to become a Zevist before being a teen, and I'm full in adulthood now. So for that I can't complain and I'm actually grateful for.
I had to fix my mentality though, the way I see food, and I healed through different workings during my teenage years. So sure thing is, after trauma, mental healing workings also help one lose weight in case of need (because there are different trauma responses, not all result in weight gain).
You gave way more detail about the situation then I did, which is extremely good, I really appreciate, as it is something that not many people talk about. The body does its best to protect itself after trauma, and that is to be noted.
There's this working I've made 5 or 6 years ago, for mental healing and strength, but after which I lost fat as well. The working goes like this:
Vibrare Ansuz x1 (while focusing on the rune's symbol)

Vibrate Thurisaz x1 (while focusing on the rune's symbol)

This above is one round, do x36 rounds in total.
Affirmation x9
"The energies of Ansuz and Thurisaz are healing me mentally, and are giving me the wisdom and strength to easily remove any obstacle which is holding me back from achieving everything I want, in the most beneficial ways for myself"
I, of course, used a lot of workings during the years to heal, and I strongly encourage everyone to try and experiment with different things, because everyone is different. I just let that working here in case anyone wants to give it a try.
Also being shamed by my family, and ridiculed to make me afraid to move my body, to not be noticed, which also resulted in weight gain. Thing which I fixed with the above working as well, and with Sowilo workings, for action, and freeing the soul with Munka.
That is why, if the weight problem in someone is mental, the source might be different and therefore healed differently. So, once again, the importance of knowing one's self, so you know how to approach the root of the problem.