Your Basal Metabolic Rate is the amount of calories your body uses per day just to remain operational. If you did nothing but lay in bed, you’d still need a good amount of calories. Check a calculator like this one to get a rough estimate of it. You’ll require more calories than that on a daily basis even if you live a pretty sedentary lifestyle. If you’re burning 500 calories per day through exercise, you’ll need to get that energy from somewhere.
You mentioned you’re trying to lose weight, so it does make sense to take in fewer calories per day than you’re burning, but don’t overdo it. Maybe take off 20% (I’m not a doctor, this is just a common number I’ve seen) from how many calories you’re taking in. I don’t know much about you, but I’m guessing that 1200 calories would lead to some serious (possibly dangerous?) weight loss (and hunger), even without the daily workout. Speaking of the daily workout, you don’t want to deprive yourself so much that your body can barely function, let alone let you effectively work out and build muscle mass. But don’t take my word for these things; I may not know what I’m talking about. Do a lot of your own research, or better yet, talk to your doctor, to decide how to proceed.
Rob has mentioned that the DRI of most micronutrients is set so that most people would be getting how much they need even if their actual intake varied a decent amount. That was part of the reasoning for getting rid of the 1800 calorie female blend: they can just have less of the standard 2000 calories version and still be fine.
Anyway, seems like Soylent will be great for you. I really appreciate knowing exactly how much energy I’m taking in, and I’m not even trying to gain or lose weight at the moment.