Of course you'll be in poorer health. You're losing weight, and if you keep it up you'll eventually starve. The process of "losing weight" has to be temporary. However, if you could determine the calorie count that would keep you stable at your desired weight, you will never be able to reach that weight on that calorie count (all else equal: no extra exercise, etc), because your body will lower metabolism enough that you'll level off above that.

I have lost weight in a sustained fashion to accomplish a goal just once in my life so far (~310 to 187 at my lowest; let's agree that I wasn't fatter at 187, eh?), and it would have taken years to drop it had I just started eating 2000 kcal a day. Even 2500 kcal is probably enough to maintain 300 lbs if you don't exercise and don't actively try to build muscle.