How is 1400kcal not a healthy amount to eat?
Not a nurtionalologist but MFP recommend against eating too low and will actually warn you if you regularly log less than a certain amount.
The theory goes that when you get below a certain level your body assumes that food is getting scarce and reacts by slowing your metabolism and increasing fat storage.
Which leads to plateauing and means that when you return to "normal" calorie intake your weight will yoyo.
That's the theory anyway.
It is (misleadingly) referred to as "starvation mode" and it is HOTLY debated on the MFP forums.
I'm not qualified to comment. All I know is that sticking to the MFP recommendation (which is ~500kcal below TDEE) has worked well for me and hasn't felt that difficult, so I'll keep doing it.