BMR and calories you eat

Remember that BMR is the calories your body burns to just be alive at total rest. (Technically it is more complicated then "the calories you'd burn if sleeping all day" as many around here will say, but this definition works well enough.) Keep in mind that you will burn more than this due to daily activity (even without exercise) so you can eat more than your BMR and lose weight as long as you maintain a caloric deficit (i.e. take in less than you burn).

As a general rule, if you find that you eat consistently below your BMR and are either (1) not losing weight effectively or (2) are feeling off (e.g. sluggish, headachey, or similiar) then you need to up your caloric intake. If you are losing effectively and feeling fine then you are probably fine as long as you stay close to or slightly over 1200 net calories.