Help! Gain weight won't stop

Here's some knowledge from a nutrition book that I'm reading, that might help you to better understand why your body is still gaining weight. I went through something similar, though not as drastic as you did after I went through a period where I was eating very little food during the day for about a year. Though I went all the way up to 136 on the scale when I started eating again.

Hunger Triggers Survival Mechanisms
When you go hungry for a prolonged period, your body reacts as it would to starvation. There are studies that show that the body has survival mechanisms that food deprivation sets into motion. One is a tendency to overeat when food becomes available again, so that your body can ready itself for the next food shortage.

That probably explains your binging, which is terrible, but I hope it makes some sense.

An example the book gives are World War I and II victims of starvation, that found it difficult to control their appetites once they were provided with good again. They would consume 4,000 or even 5,000 calories a day, and many of them became obese.

Looks like it's the body's natural instinct to take in as much food as possible when it's available again. Which, I guess since it's a natural function, it's pretty hard to ignore. What I would do is just make sure you're taking in the right kinds of foods, so that your weight gain is as little as possible. Whole grains, fruit, veggies, as little processed food as possible. I imagine that will help you

As for why you're gaining weight still, the book says that people who went through starvation/semi starvation (very low calorie diets), can experience improved efficiency of their intestines. So their intestines become better at pulling the nutrients from the foods you eat. Thus, when you start eating again, you gain weight more quickly.

Again, if you eat the right kinds of things; stay away or just limit fat heavy foods like oils or dairy, it's possible you will have less of a gain at the end of your recovery.

Your metabolism also lowers when you going into starvation mode. It means that you burn less calories while you're resting, and when your exercising. It's another way for your body to try and conserve what energy it has left. So you have to give it a chance to pick up again and start working normally. I have no idea how long that takes. You'd have to ask a doctor to answer that question for you Or maybe look it up on the internet.

So I hope that answers a few of your questions as to why your body is doing what it is. You were starving yourself, so your body turned on it's natural mechanisms to help you survive longer and use your food more efficiently. The more you dieted, the more efficient your body became at storing and using the food you ate. So weight gain is happening, and weight loss will be slower. Your body is much less reluctant to let go of the calories you're giving it now.

I'd say you just have to give it some time to adjust to the fact that you're not going hungry anymore. Once it gets used to it, I'd say everything will even out again. People recover from this, and there's no reason you shouldn't, either. It just takes time. The advice I would give you would be to try and relax. Realize you're recovering from a disorder, and that nothing happens immediately.

I wish you the best in recovering from what you went through. I have been struggling with obsessing over my food for a few years now, and like I said, I went through some of the starvation that you went through. So I can understand it in a small way. I hope my advice helps you in some way

But why am I gaining weight right now even if I eat no more than 1200 calories?

Because you've killed your muscle mass, and that means whole lot less glucose stores possible.
Both if which would add to lean body mass (non-fat mass), and increase metabolism if you had them.

You probably also have a shot metabolism besides that effect.

As such, until you build up your muscle mass, you are eating at maintenance right now. So it don't take much for your body to see a surplus.

Your only exercise should be heavy lifting.

And you'll have to except the fact you will gain weight, muscle and glucose/water, and some fat, while eating enough to actually rebuild what you have lost.

You are in prime position for a very frustrating life-time of yo-yo dieting, because you are starting out young with probably a whole lot less muscle than average.

Actually, while you start lifting, you could probably increase calories up to a level that would match what your body really could handle, probably more than then 1200, but it won't be at normal levels for someone your age, weight, height.

It would probably be a great advantage to get a bodyfat % test, hydrostatic or Bodpod or DEXA scan if you have the money, and know what your metabolism could be based on that LBM.
You could probably increase your metabolism somewhat.