index of the general level of activity of an individual's body metabolism, determined by measuring his oxygen intake in the basal state—i.e., during absolute rest, but not sleep, 14 to 18 hours after eating. The higher the amount of oxygen consumed in a certain time interval, the more active is the oxidative process of the body and the higher is the rate of body metabolism. The BMR has been used in measuring the general metabolic state during therapy. It was formerly widely used to assess thyroid function (thyroid function test), since the thyroid hormones are prime regulators of tissue oxidation and metabolism; but, since the advent of radioactive-isotope tests and thyroid-hormone studies, BMR measurements have fallen into disuse.