The Resting Metabolic Rate (RMR) test measures the amount of energy your body is using when at rest, which means when you’re relaxed and still. Your RMR is measured by analyzing the amount of oxygen used by your body after you have fasted and avoided exercise for 12 hours. The machine, called an indirect calorimeter, is accurate within five percent.
Learning your RMR can tell you if you have an increased or decreased metabolism. This information can guide you in determining the amount of calories you need to eat each day to achieve your goal, whether it’s to lose weight or gain it.
The RMR has a larger range than most people realize, and there can be surprises. It might suggest that you be referred to a doctor to test for an underlying disorder, such as an undetected thyroid issue. And it can help you understand how it all works together.
For example, I’ve had patients who look skinny, but their metabolism is actually pretty low. Often this is because they lack muscle mass. If you have more lean tissue, your metabolism is higher because muscle at rest is more metabolically active than fat tissue. This is good news for many people, because it means you can change your metabolism over time by building lean tissue.
This can also be helpful for people who have been yo-yo dieting for much of their life. The interpretation of results can provide realistic expectations of what to expect in their pursuit in getting to a healthy weight. It will put it into perspective if they need to focus more on exercise, nutrition or both.
Women in particular can benefit from this information. Often women don’t want to build muscle because they’re afraid of bulking up. But using resistance training, you can develop more tone and definition rather than more muscle. So you change your metabolism by changing the ratio of body fat to muscle.
This can also help people understand why dieting so often fails in the long-term. If you follow such a low-calorie diet that you’re actually losing lean tissue along with body fat, this can trigger your body to lower it’s RMR as it goes into starvation mode. The scale shows you’re losing weight, but your body composition changes, so your metabolism tanks. Then when you start eating again, you store it as fat.
This is why most registered dietitians recommend slow weight loss combined with vigorous resisted exercise for long-term weight loss.
We can use the RMR not just to figure out nutrition intake, but to calculate if additional or different exercise routines are needed, too. People trying to lose weight tend to do all cardio, because it burns way more calories. Weight training doesn’t burn half as many, but benefits your metabolism in a longer, more sustainable way. In the end, you’ll be able to eat more and maintain weight and won’t going from diet to diet anymore. Weight training is also cardiovascular work – especially if it is vigorous. And daily metabolism (not resting) increases post exercise for many hours, especially with strength training.
Retesting your RMR over time can provide guidance as to whether your exercise and nutrition program is influencing your metabolism for the better. This is why health coaching programs such as the Personal Health Coach Programs at Kaiser Permanente may test RMR a second time to determine if your strategies are working or need to be tweaked for better results.
RMR can also be useful for athletes who want a calorie budget to meet their high energy needs. With this information, a sports dietitian can calculate their macronutrients (“macros”) and guide them towards the best food choices for optimal training and race day fueling.
The bottom line: RMR results can be an eye opener and a fun fact to use in the pursuit of optimal health and fitness.
To find out more about the Personal Health Coach Program at Kaiser Permanente San Francisco, which is open to non-members as well as members, call 415-833-7800.