I have a question on maintaining weight. I've checked calculators out and my maintenance is about 2,700 calories per day. For the entire time I've been losing weight, I've been on a 500 to 1,000 calorie a day deficit.

Wouldn't that have "trained" my body into thinking that my deficit intake is now my current intake since I've been on it so long? I'm worried if I actually start eating a recommended maintenance intake I will gain weight, since it's 500 calories over what I've been doing to lose.

So, how does my body know that 2,700 calories is maintenance, and 2,000 (for example) is not?

My understanding of those calculators is that it's supposed to give an estimate of what your body burns every day just to exist. Basically just your organs functioning, breathing, etc. And you can also put in your activity level so that's taken into consideration as well. So if you burn 2700 calories just living a regular day, you could eat 2700 and maintain your weight. To lose weight and create a 500 calorie deficit you'd eat 2200 a day. Of course the calculators are just an estimate and everyone's body is different, so you'll probably have to adjust up or down based on how your body reacts.

Right, but how is my body supposed to know that 2,700 is my maintenance?

I'm moderately active, so it says "2,700 for maintenance", but I've been eating about 2,000 per day to lose weight. So, since my body is so used to eating at 2,000 a day for so long now, wouldn't I have essentially trained it into thinking 2,000 a day is now a maintenance level?

Just because you're only eating 2,000 calories a day doesn't mean your body is going to think, "Hey, that's all I'm taking in.. guess that's all I'll burn!" It doesn't really work like that. Your basal metabolic rate is the amount of energy your body needs just to keep it functioning. As long as you don't cut calories severely and eat at least enough to keep your vital organs working, it's not very likely that your BMR will slow down on its own. Shaving 700 calories off your intake isn't anything drastic, so you should be just fine. Your body should be more than happy to burn fat for any additional fuel needs it has.

If your body thought 2,000 was maintenance then you wouldn't be losing weight, you'd be maintaining. That said those calculators are just an estimate and most maintainers will recommend that you started add calories back slowly, 50-100 per day per week until you stop losing weight. Your thought process is partially correct, if you stay at a very low cal diet for too long it can be difficult to add cals without gaining, but eventually your metabolism will bounce back.