All day your metabolism churns away, converting food to fuel throughout your body so everything—from your circulatory system to your hormones and heart to your bones and brain—can do their jobs, says Michael Rosenbaum, MD, professor of pediatrics and medicine at Columbia University Medical Center in New York City. Yet, mention metabolism and most of us think first of our waistlines. We blame it for that extra bit of belly fat or praise it for allowing us to eat anything without adding pounds. Is metabolism really the master of our weight?
The pace at which your metabolism naturally works is called basal or resting metabolic rate, and everyone’s is different. “It’s the rate at which the body uses energy to perform its functions,” says William S. Yancy Jr., MD, program director of the Diet and Fitness Center at Duke University. Simply put, your basal metabolic rate (BMR) is the number of calories your body would burn if you stayed in bed all day, and on average, it accounts for about 50 to 60 percent of your daily calorie expenditure. You can’t easily change your BMR, which is determined by genes, age, gender, height, weight, the amount of muscle you naturally have and your thyroid hormones. But you can boost your daily energy expenditure—aka calorie burning—by being more physically active.