Attempting to understand BMR and RMR

All this calories in-calories out thing has led me to try to delve deeper into what BMR and RMR are and what they mean to me in relation to my weight loss.  I've heard of them, but they've never really meant anything to me.  In general, they may not in my everyday journey, but I still felt it was important to know what they are.

Obviously these are all estimates and don't take all factors of your individual activity or body mass into consideration, but I think they're still good to help you see what your caloric expenditure would be just resting all day in comparison to the calories you take in  and the exercise you do.  For me, it further shows the difference between my BMR/RMR and recommended calories for weight loss, especially in relation to calories expended doing exercise and how divergent these numbers are from the BMR/RMR calculations.

Make sense?  No?  I didn't think so.  Okay, so here is the breakdown:


This site talks about BMR and RMR and their similarities and differences and how to calculate them both.  This is what they say about them both:

• BMR stands for Basal Metabolic Rate, and is synonymous with Basal Energy Expenditure or BEE. BMR measurements are typically taken in a darkened room upon waking after 8 hours of sleep; 12 hours of fasting to ensure that the digestive system is inactive; and with the subject resting in a reclining position.

• RMR stands for Resting Metabolic Rate, and is synonymous with Resting Energy Expenditure or REE. RMR measurements are typically taken under less restricted conditions than BMR, and do not require that the subject spend the night sleeping in the test facility prior to testing.

Probably all of us have heard of BMR, but if you're like me, RMR is not quite as common a term.

The site provides calculations to determine what your caloric intake should be if you are simply at rest for 24 hours.  The first is the Harris-Benedict* equation for BMR:

• For men: (13.75 x w) + (5 x h) - (6.76 x a) + 66
• For women: (9.56 x w) + (1.85 x h) - (4.68 x a) + 655

 Based on this formula, my numbers look like this:

(86.8 kg x 9.56 = 830) + (170.18 cm x 1.85 = 315) + (48 x 4.68 = 225) + 655 = 2,025

This site also says that the Harris-Benedict typically overestimates by 5 percent or more.  Subtracting 5 percent from 2,025 is 101, which then brings the number to 1,924.

The other calculator is the Mufflin* equation for RMR:

• For men: (10 x w) + (6.25 x h) - (5 x a) + 5
• For women: (10 x w) + (6.25 x h) - (5 x a) - 161

Based on this formula, my numbers look like this:

(86.8 x 10 = 868) + (170.18 x 6.25 = 1,064) + (48 x 5 = 240) - 161 = 2,011

(*Please note these two calculations are done in metrics: w = weight in kg; h = height in cm; a = age)

What I take away from all this math is this:

Harris-Benedict:  2,025 (or 1,924 based on the overestimation)

Mufflin:  2,011

This shows that they're pretty close (even with the overestimation of the Harris-Benedict test).  So, when my LoseIt! or other apps tell me that, in order to diet, I should be taking in 1,225 calories, it's understandable to me now that if my net calories for the day are less than 500 (calories in minus calories through exercise), that my body would go into a form of self-preservation "shock" and stop losing, resulting in plateaus.  This is why I MUST either scale back on my exercise or increase my caloric intake.

And if I've kept your interest thus far, I hope you've learned something today, class.  :)


**Information retrieved from Caloriesperhour.com