RMR. The Key To Your Calorie Intake


RMR stands for resting metabolic rate.  RMR by definition is the number of calories your body burns at rest to maintain normal body functions and structures.  These structures include but are not limited to muscle tissue, hormones, antibodies, collagen, and many of the bodies vital organs.  Your RMR generally accounts for between 60-75% of your body’s overall calories used in a day.

Your RMR is determined by a number of factors.  They include your age, height, gender, amount and type of physical activity performed regularly, dietary habits, environmental temperature, and most importantly your muscle mass.  Muscle mass is the key determinant in determining how many calories you burn at rest because this is where most of your calories are “burned”.  Think of muscle as an engine.  I know everyone is going green to become more fuel efficient but if your goal is weight loss the last thing you want is a fuel efficient engine.  You want your muscle to become a large eight cylinder engine burning lots of fuel (i.e. calories).  This does not mean you need to have large muscles but more specifically highly metabolic muscle that is capable of burning lots of calories at rest.

In my experience, individuals who regularly perform weight training have the highest RMR’s.  Weight training has been shown to significantly elevate RMR more than most forms of cardiovascular exercise.  Cardiovascular exercise performed at high intensities such as sprint and interval training being the exception.  The bottom line is the more intense the exercise, the greater effect on your RMR.

So why would you want to have a higher RMR?  It’s quite simple if you are trying to lose weight.  You will burn more calories at rest.  It is possible that if you never change your diet but elevate your RMR you will experience weight loss.
Be careful.  I’ve often seen people who start exercising more intensely rapidly increase their RMR and start eating uncontrollably leading to a gain in weight.  This can result from a higher metabolic rate causing more cravings throughout the day.  If you fail to eat balanced meals and go for high carbohydrate foods you may find yourself craving food all day long as result of erratic blood sugar levels.  I strongly recommend anyone considering exercising more frequently and/or more intensely to meet with a sports nutrition coach to help design a nutrition plan to prevent these cravings.

The single #1 mistake I see many people make is once they find out their RMR, they eat below this number.  Remember earlier I mentioned RMR is the minimum amount of calories you need to sustain vital structures in the body such as lean muscle, hormones and antibodies?  If you fail to give the body the calories it requires, your body will be forced to breakdown these structures and use them as an alternative form of energy.  Will you lose weight?  Absolutely.  Is it the right weight?  Probably not.  Calorie restricted eating often results in a loss of muscle.  Loss of muscle can result in a smaller engine that doesn’t burn much fuel.  Remember, if your goal is weight loss, you want muscle that burns as much fuel as possible. You’ll have to pay more for your fuel (your grocery bill…not your gasoline!) but it’s a small price to pay for your health.

The correct way to experience weight loss and maintain your muscle is to first determine your total daily energy expenditure.  This equates to your RMR + everything else you do in the day that requires calories.  Exercise, work, playing with the kids, doing laundry, or simply getting out of bed all adds to your total daily energy expenditure.  The ideal calorie intake is somewhere between the RMR and your total daily energy expenditure.  This assures weight loss (more specifically fat loss) but the preservation of muscle and other structures in the body thus leading to better health.  Weight may come off slower but over the long haul you stand a much greater chance of getting to that ideal weight you may desire.  Instead of becoming harder to see weight loss over time, it is just the opposite.  Unlike most calorie restricted plans, weight loss will occur slower at first but pickup a lot of momentum as you start to see results over time.  This is because you are not losing muscle with calorie restriction and you are elevating your RMR at the same time…not slowing it down.

How do you determine your RMR?  There are many different ways.  The most popular and inexpensive method I have seen is using a device such as the BodyGem™ which is a breathing device measuring the amount of oxygen you breath in at rest, a process known as indirect calorimetry.  There are also RMR calculators online you can try to estimate your RMR but I have found them to be inaccurate in many cases.  My personal RMR was off by over 500 calories on one site as compared to the Bodygem™.  I also recommend retests after 3-4 months to show people the progress they are making and that all the exercise they are doing is paying off.

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