RMR

I had an RMR test done the other day. my result was 1750. I am trying to figure out a good range to stay under to lose consistently. Right now I have MFP calories set at 1750. Would it be safe to say if I ate under that I should always lose or is that too simple? I would say I am slightly active, I workout 2-3 days a week (usually 2) and work 1 12 hr busy shift on my feet all day once a week... Any insight?