NEVER eat at your BMR or below it... ESPECIALLY if you exercise. what you're doing is tiring out your body. for instance, my BMR is 1376 cals. if i did a normal weight/cardio routine my body would be exhausted because i need to eat 1376 cals JUST for my body to keep my organs functioning. and actually, been there and done that. i was miserable and cranky.

and whoever said a calorie isn't a calorie is SOOO right... which is why low carb/high fat works at maintenance calories. i'm a strong proponent of eating low carb near maintenance cals - don't drop cals until you've exhausted every other avenue (cardio, etc).