I am interested in having my resting metabolic rate tested to get a better sense of where my calories should be, and I found a place near me that does the testing ($99; they also do DEXA scans for $129). My question is about timing. I'm only 18 days post-op -- would it make more sense to test when I am closer to my goal (whatever that is) because it may change significantly as I lose weight? Would appreciate anyone's opinion and information about this!

For now I would wait. You are not able to consume enough calories. A trainer would use your resting metabolic rate to calculate how many calories you burn without exercise to help you determine what is the optimal amount of calories for you to consume daily and lose weight. (or something like that) At this point this is pretty much predetermined by the surgery.