What's the Difference Between RMR and BMR?

When looking to lose weight, there are a lot of questions to answer—primarily in regard to what works best for you and your body. How much should you eat? When should you work out, and what exercises should you do? How do you balance food and exercise to reach your goals?

Start with the basics: Your basal metabolic rate (BMR) and resting metabolic rate (RMR) are two simple numbers that can help answer some of your questions. Learn more about what these numbers mean, how to calculate them, and how they can be used to reach your weight loss goals.

The Difference Between RMR and BMR

Sometimes used interchangeably, RMR and BMR are standard measurements of how much energy your body uses. You may also have seen them referred to as “resting energy expenditure” and “basal energy expenditure.” However, the two are slightly different:

  • RMR (resting metabolic rate) measures the number of calories your body burns while at rest
  • BMR (basal metabolic rate) measures the minimum number of calories your body needs to perform its most basic functions—like breathing, producing cells, maintaining temperature, etc.

They sound similar, and measuring either your RMR or BMR will provide a good baseline for your body’s energy needs. The primary difference is that, based on how it’s measured, your BMR is considered a more accurate calculation.

So, Why Measure RMR and BMR?

Think of your body as a machine that needs fuel in order to operate. And, like any other machine, you’ll need more or less fuel based on the amount of work you want it to do. Your RMR and BMR are the amount of fuel it takes for your machine just to stay up and running.

To lose weight, you’ll want to include exercise, which means your “body-machine” requires harder work and more fuel. And since fuel comes from our diet, calories are how we measure the actual amount of energy we get from what we eat and drink.

We’ve all heard of calories and understand they play an important role in managing our weight. But they’re not necessarily the enemy: they’re the source that keeps your body-machine in operation. How many calories your body needs depends on your sex, age, size, level of activity, and more.

Therefore, measuring your RMR and BMR helps you first determine your baseline daily caloric intake and then make adjustments based on whether you want to gain, lose, or maintain your weight.

How to Measure Your RMR and BMR

You have a few different options when it comes to measuring your RMR and BMR. Both can be tested in a clinical setting under specific conditions. Finding your BMR usually occurs after at least eight hours of sleep and a (minimum) 12-hour fast from food, caffeine, or other stimulants. The test typically takes place in a dark room and in a reclined position. Under these conditions, your body is as close to a naturally restful state as possible.

Finding your RMR is more relaxed in that it can be done without as much sleep or fasting beforehand. This is also why BMR is considered more accurate, but either measurement will give you a personalized idea of your body’s caloric needs.

Aside from clinical testing, you can calculate your numbers with equations that use your personal measurements (height, weight, etc.) to determine your energy needs. There are also websites that will crunch the numbers for you, but results vary by site and might not be as reliable as clinical—or your own—calculations.

Using RMR and BMR for Weight Loss

Once you know your body’s natural energy output, you can use the numbers to help reach your weight loss goals. Track your what you eat and drink in a day (nutritional input); subtract your RMR/BMR (energy output); and subtract your calories burned during exercise. The resulting number, if negative, means weight lost.

Seem complicated? It’s easier when you have the numbers. Here’s an example:

  • Nutritional input = 2,000 calories consumed
  • BMR = 1,600 calories burned
  • 30 minutes of jogging = 300 calories burned
  • 30 minutes of weight/resistance training = 150 calories burned
  • 2,000 – 1,600 – 300 – 150 = -50 calories consumed

These are fake numbers, but they still show the role your RMR/BMR play in weight loss. Running your own numbers means keeping track of how many calories you’re taking in versus how many you’re using up, but don’t be overwhelmed. While losing weight seems like hard work, think of it as just another number.

How Many Calories is One Pound?

There are an estimated 3,500 calories in one pound of fat: therefore, burning about 3,500 calories is equal to losing one pound. By creating a deficit of 500 calories per day, you can lose one pound in one week. That deficit, over time, will help you shed pounds and reach your desired weight.

What’s Next?

We know: at this point, weight loss seems more like math and science, but it doesn’t have to be complicated. Measuring your RMR and BMR will give you a good starting point for your weight loss journey, and it’s something you can do whenever you’re ready.

Just remember that the process is different for every body, and personalizing your routine will better enable you to make it a lifestyle. The numbers and calculations will change based on your body, specific needs, and desired goals  and the whole journey is much more enjoyable when you do what’s right for you.

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