If it's been consistent, it indeed can.

if it was mainly undereating with spikes here and there, no, the excess for the time then was stored as fat. Because body figures the craziness will continue, so get the fat stores on just in case.

But you are aware you'd have to eat 3500 calories OVER maintenance to gain 1, ONE, pound of fat.

For instance, 3 weeks you say. "Ton of fat" is hyperbole obviously and a tad concerning, because you should know exactly how much the weight went up, not by looking in mirror, can't tell that way, not fast gain.

But say "ton of fat" was 6 lbs.

6 x 3500 = 21000 excess calories over 3 weeks or 21 days.

21000 / 21 days = 1000 calories daily in excess, over NOT your eating goal, but rather over your TDEE, or maintenance.

Where you eating 1000 extra calories over your maintenance daily on average? So if maintenance is 2000, you'd have to eat 3000. If you exercised, maintenance was higher that day.

If yes, and self-control is that bad, you need to talk to a counselor.

Being able to eat more than bare unsafe minimum usually means you can plan stuff out, and allow yourself some "bad" stuff. But if you have a problem with not being able to eat just a little, then obviously better to forget it.

Like if you can't measure out a serving of chips and stick to it - then don't start it. Same with desserts, if you can't be satisfied with a little, then don't have any.
If cravings and lack of control are related to eating high carb items, then don't do it.

Part of that could be from still under-eating for what your body wants. You fight it until you give in. Fix is not to undereat in the first place.

And how do you know exactly what you've gained between fat and water?
Perhaps you are convinced without any actual knowledge of how you could tell one from another, so convince me.

To me it sounds like you have an unhealthy relationship with food at this point... I would not continue to overeat and then try to shock your body into weight loss by suddenly dropping calories, but instead, go about it in more of a deliberate way.

Have you figured out your TDEE so that you know what your daily requirements actually are? I would start there and find out what your calorie intake should actually be.

Since you have come from what sounds like a very inconsistent history, I would try to figure out your TDEE and then eat at that level (not over) for 8 to 12 weeks. Coming from a VLCD history, you may see some gains as your body adjusts (especially if you immediately jump up to this level - which it sounds like you have already done).

Once your body is comfortable with the fact that those wild fluctuations in intake will not continue, your weight should stabilize and then at that point you would be ready for a cut. You would want that cut to be a moderate 15% cut, not something like dramatically dropping from 3,000 to 2,000 as you had mentioned.

The whole idea is to find your TDEE and know what your body's requirements are, then use that number to gauge your intake, adjusting as necessary for changes in exercise.

Personally, rather than continuing to overeat, I would find your TDEE and try to eat at (not over) that number consistently - try to get a healthier relationship with food, rather than eating "uncontrollably". Once you feel like you are in control and your body has stabilized, that is when you would start that moderate 15% cut.

You know why fat is the body's preferred method for dense energy storage - very little water stored with it, very minor.
If your body had to store the energy of 1 lb of fat, 3500 calories, as carbs which must store with water, it would weigh 7 lbs, and take up a lot more space.
It'll store wherever there is muscle.

Fat just depends on you, as to where it store first. You obviously have gained some eating that much over TDEE, which I recall wasn't that high.

Love learning new things!

Okay so I'll eat 2000 starting tomorrow and keep eating that for the next three months?

Is 2,000 what you have calculated your TDEE to be? If so, then yes, drop to TDEE and try to be as consistent as you can eating at that level. Three months would be great, allowing your body time to acclimate. Because you come from a history of VLCDing, even at TDEE (theoretically maintenance) your weight may fluctuate as the body adapts to the new level of intake.