The problem is it can only ever give an average. I presume whoever told you your BMR did a respiration based test which is specific to you...
The important question however is are you losing weight as it is and are you happy with your loss speed as it stands?
42" jeans(25/01/2013) 40"(28/02/2013) 38"(20/03/2013) 36"(25/05/2013)
Down from 60" waist jeans since June 21st 2012.
Still keeping to my 26" jeans, but they are too tight for comfort. too many tasty things in the US, and over Xmas.
Onwards and Downwards! http://www.menu52.com/