Originally Posted by SField
And what about metabolic rate?
Most accurate method is probably going to be direct calorimetry where you put someone in a chamber and measure energy as the amount of heat released.
The most common method is probably going to be some kind of indirect calorimetry, which measures oxygen consumption, which can then be used to calculate caloric expenditure. There are various devices out there that can take pretty accurate measurements. Keep in mind you have to follow a strict protocol to get true BMR (including taking measurements shortly after waking, after an overnight fast). If they offer it at your gym it is probably not truly BMR, but resting metabolic rate.
The following device was being marketed pretty heavily to gyms to measure RMR and it's pretty easy to use. I'm not sure on the accuracy. There use to be a bunch on ebay that were pretty cheap when the company went under (before someone bought it out and released it again).http://metabolicratetest.com/