How to Use RMR Data to Change Your Body Composition

Shannon Miller

October 29, 2021


Metabolism: the driver of energy balance in the body. It controls how food is processed into energy or stored in the body for future fuel. It also directly factors into body composition, or the proportion of fat mass versus lean muscle mass in the body. Metabolism can be quantified through specific testing that can in-turn inform a plan to change body composition over time. How exactly? Read on to learn why RMR data are necessary when it comes to making sustainable changes in body composition.

Body composition, or the proportion of fat mass and lean muscle mass in the body, is largely dictated by nutrition, and significantly supported through fitness. The metabolism dictates much of how energy is utilized by the body through the consumption of calories either through exercise, lifestyle activities, or basic bodily functions. The latter refers to an individual’s “resting metabolic rate” (RMR) or the number of calories burned each day while at rest. While this number is considerably “fixed” through genetics, there is still a portion that can be altered (sped up or slowed down) based on lifestyle factors like exercise, nutrition, and hydration.

To calculate RMR, a simple, quick and non-invasive breathing test is administered to measure the rate of oxygen consumption in the body. This number helps inform daily caloric intake range required to reach a specific body composition goal, whether it be to lose, gain, or maintain weight. Body composition is most accurately measured through a DEXA scan, which measures fat mass, lean muscle mass, bone density and visceral fat. Most often, to improve body composition, the loss of fat mass and the gain (or maintenance) of lean muscle mass is required.

To accomplish this, the following steps are typically taken:

  1. Obtain baseline metabolism & body composition measurements (RMR + DEXA)
  2. Interpret caloric intake and use RMR & DEXA data to establish an appropriate body composition goal
  3. Follow a nutrition plan that adheres to RMR data (daily caloric intake range)
  4. Retest RMR & DEXA to examine changes in body composition & metabolism

Exploring a hypothetical case study can be helpful in painting a picture of how data from an RMR test can help inform a plan to change body composition over time. For example, after taking an RMR, Client A* establishes a baseline measurement of 1490 calories. This means, to maintain their body composition, they must eat close to 1490 calories each day. RMR data also provide a calorie range in order to lose weight that is typically 10-15% less calories than the maintenance range. If Client A follows a nutrition protocol of limiting caloric intake to 1350 calories a day, this slight caloric deficit over time may result in the loss of fat mass, and if Client A apply the appropriate type of exercise (resistance training), they can increase or maintain their lean muscle mass. A repeat DEXA scan can confirm body composition changes in Client A by assessing changes in the proportion of fat mass compared to lean muscle mass. Typical changes in body composition are apparent after anywhere from 6-12 weeks after following a specific nutrition and exercise plan.

What’s more, turns out body composition can also affect metabolic rate. Generally, the higher proportion of lean muscle mass compared to fat mass in the body can elevate the metabolism. This is because muscle tissue burns more calories at rest than fat tissue. So, should Client A receive a follow-up RMR test after significant changes in body composition (an increase in muscle mass and a decrease in fat mass), they may see their metabolism speed up (their RMR range may increase).

Making sustainable, long-term body composition changes requires more than guesswork. Online calculators that “measure” RMR often come with inaccuracies, as do many common at-home body composition scales on the market. The only way to obtain full picture of metabolism and body composition is to lean on proven, accurate technology that provides solid data to inform a plan to reach your goals.

Interested in learning more about your unique metabolism and how to achieve your optimal body composition? Schedule RMR & DEXA tests and speak to our expert Nutrition Coaches!

*This is a hypothetical case based on controlled settings. Individual results may vary.


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