Questions! Help :)

mbfowler87

I have a few questions. I recently started doing crossfit, which is essentially cardio-strengthening. I wear my HR monitor and have an app to calculate my calorie burn based on avg HR, weight, and time spent exercising. Even though it is "strength" is this an accurate way to determine my calorie burn? I have always used my HR monitor for running and kickboxing calorie burns but have never used it with strength.

Also, I am 25 y.o. 5'3 and 142lb. MFP has my calories set at 1200, which seems low to me because my BMR is about 1300. I am an RN who walks a lot at work and I usually workout once a day on my days off. I am afraid I am eating too little at 1200 calories and will plateau and have no where to go from there when it comes to changing my weight loss plan. Any recommendations? I have been losing weight, about 3 lb in 3 weeks and need to take my measurements (been slack on that) Open to any and all suggestions! Thanks!