Increasing calories in recovery

Why not gradually increase calories? Since you are using a nutritionist, perhaps ask that person, if you haven't already.

Your metabolism may be a little slow at the beginning of recovery however, that will change drastically! My outpatient nutritionist, who specializes in eating disorders, explained to me that a 400cal jump each week is really good for kick starting the metabolism. But when I was in the hospital, they had me on 3500-4000+ cals a day but they did their cal increases every couple days. When I went there I was doing around the same amount of cals as you so it took a bit to get up to that much. When your body gets used to having nutrients, it starts to suck them up quickly and you go into a hypermetabolic state. It's uncomfortable but some of they symptoms I had personally were major hot flashes and ravenous hunger all the time. There was a point I got stuck in a wheel chair upped in cals because I started losing weight on the 3500cal plan when I got to that state. Once you get to the "target weight" they give you then you can cut back quite a bit and you'll get a new plan. One thing, I would absolutely NOT go straight from 800 to over 2000 if you've been restricting for a long time. And if you're ok at 2000 then do smaller increases so you don't get refeeding syndrome. 3000 will make you gain weight very slightly more rapidly, it's honestly not going to make much of a difference. A lot of weight gain at first is from retaining water. Hang in there xo

I don't believe in this "messed up metabolism" stuff. We evolved to deal with feasting/starving; we've never had regular meals continuously, so I don't think what you are doing is going to have any effect physically.

Now, psychologically perhaps...but I don't know anything about that.

You say you are worried that you will have "much more rapid weight gain", but I am assuming you are supposed to be eating more because you need to gain weight, so what's the big deal? You aren't going to put on 10 lbs overnight. It takes an EXCESS (over and above what your body is using) of about 3500 calories to gain one pound, so there is no way you are suddenly going to pack on too much weight for you to keep track of (although don't forget about water - read the very important sticky post on the nutrition and weight loss forum about "eating more than your cut" or something like that).

Up your calories, weigh yourself regularly, slow down your caloric intake as you approach your goal weight. then maintain. It's simple math. Don't let it seem more complicated than it is.

A "messed up metabolism" is very real, there are many studies to support it, including the Minnesota starvation study which found decreases of up to 40% in metabolism. It is only makes sense evolutionary as well, if you're starving, the best thing the body could do is slow it's metabolism as to slow the starvation process itself.

I agree with everything else though, the point to recovery is one that a) is slowly progressive and b)is best in terms of recomposition--your putting on a good ratio of muscle to fat.