Basal Metabolic Rate (BMR)
In a previous article I brought up a concept known as basal metabolic rate (BMR), and if this is something you understand then great, you are one step ahead. However, I am willing to bet that there are some misconceptions you may hold, as well as some inaccurate beliefs that were taught to many of us at one point in our lives.
What is our BMR?
For those that don’t know what the BMR is, it is the number of calories required to maintain all basic life sustaining processes within the human body. The BMR alone makes up roughly 70% of what is known as our TDEE, or Total Daily Energy Expenditure. The TDEE is essentially the total amount of calories we use in a day. It includes what our body needs at our baseline (aka basal) along with any additional energy used to do anything from lifting weights to something as simple as fidgeting your fingers.
Why is this important?
The first reason is for what I just said above, it makes up 70% of every calorie used in your body. The second and better reason, is that it is always important to know how your own body works. Trying to pursue any goal involving exercise and nutrition without first understanding the fundamentals of your own body is a fool’s errand. Knowing where most of your calories are spent will help you focus on the best tools and strategies to help optimize your goals.
Another reason as to why this is important is depending on your goals, whether it is to lose or gain weight, you must either be in an energy balance positive or negative state as I’ve mentioned in a previous post. However, if I was a betting man most people have no idea how much energy (calories) their bodies use in a day in order to determine this balance. So, in order to calculate this, we would have to use an equation to determine our basal metabolic rate. Below you will see what is known as the Mifflin St. Jeor Equation. There are different equations, but based off of my research this seems to be the most accurate one. If you find something different or noticed that the literature has changed, let me know and I am happy to update this. Otherwise, this is the best equation at this time.
How do we determine what our BMR is?
Now that we’ve discussed what our BMR is and why it is important, it’s time to learn how to actually calculate it. This is the first and largest pillar of our energy expenditure understanding. I have written out the equation below so you can visualize it however I have also attached a link to a website I have used for years now. If you don’t like this one look for any calculator that uses the Mifflin St. Jeor Equation. I also highly recommend the calculator off the Mind Pump Media website. Great group of people whom are very knowledgeable on exercise and nutrition.
For those of you that need to see and visualize the equations I have placed them below. I have included ones for both men and women based off of their physical metrics. Note that the difference in the last number between men and women is mainly attributed to hormonal differences. Also remember that this number is the energy you use doing absolutely NOTHING. These are the calories that keep you alive, so from day to day you will likely burn more calories.
Men:
BMR = (10 x weight [kg]) + (6.25 x height [cm]) – (5 x age [years]) + 5
Women:
BMR = (10 x weight [kg]) + (6.25 x height [cm]) – (5 x age [years]) – 161
So for example, if we had to calculate the BMR of a 32 year old female who weighs 140 pounds and has a height of 64 inches, we would first want to convert pounds to kilos and height to centimeters. This would give us 63.6 kilograms, and 163 cm. Plugging that in we get:
BMR = (10 x 63.6) + (6.25 x163) – (5 x 32) – 161
BMR = 636 + 1019 – 160 – 161 = 1334 calories / day
Again, I recognize that likely no one is going to sit here and plug numbers into their calculator so here are two links to websites I personally like to use for friends, family, and clients I have worked with. The first one is a simple BMR calculator that also adjusts for activity levels. Additionally, it has some great bullet points on what we discussed along with other details i’ll cover in subsequent posts. The second one is also a calculator offering a relatively accurate read on your TDEE that takes into account your goals involving macronutrients. But don’t worry about macros yet if that sounds like a lot. There will be a separate post for this.
Everyone should know “their number,” or at least have a general idea of what it is. Going on throughout life without knowing your BMR or how many calories your body uses in a day puts you at a huge disadvantage. That number alone can equip you with enough knowledge to navigate your fitness goals. Knowing this number should be just as important as knowing your phone number, your social security, your address. After all, it is unique to you and only you. We put so much energy in our life towards knowing all these details about everything else but ourselves. At the bare minimum we must know how our own body functions at a basic foundational level.
What variables affect our BMR? And how can we make them work for us?
Some of you may think that mean weight loss is out of your control since we have been taught that our “metabolism” is what we are born with and cannot change it. I’m here to tell you that is completely false. There are key fundamental steps we can take to actually make the body work towards your advantage. And beyond the caloric benefits of exercise there is also a vast number of benefits involving the cardiovascular, endocrine, and musculoskeletal system.
Our BMR can be altered by a variety of things and I can list them like every other website but I find many of their reasons vague, non-quantifiable, and often useless. Speaking from a background of research I can say that the TWO main things that can dramatically alter our BMR with confidence is having more mass ideally in the form of lean muscle, and sleep. This is well supported by modern research and up to date understandings of the human body. Remember, my goal here is to keep things as simple and indisputable as possible. However, this a dynamic field where research and data can change and show us better practices down the road.
There is strong evidence that simply getting 7 or more hours of quality sleep can increase levels of testosterone in men and women. This is a major player for our BMR. In general sleep is critical for hormone balance. After all, sleep is the time your body puts towards repairs from “damage” or work done over the day. One study depicted a 15% drop in testosterone levels after 1 week of 6 or less hours of sleep. That is incredibly significant. I have a post all about sleep with deeper discussion into this research that I recommend you read. For now, I will leave this here for simplicity. I understand we have busy lives, but one sure-fire way to increase your BMR, overall calorie usage, and lifespan is to increase sleep
Finally, I can and will write many posts about this because of its importance. Exercise, specifically resistance training that will build lean muscle is the largest key to increasing BMR. I would challenge anyone to dispute this. The data and research is irrevocable. Even if the data was not there, you learned about the basic principles of the human body and the concept of more mass requires more energy. We discussed the effect of total mass on BMR previously, however we also noted that most people desire the mass to be in the form of lean muscle both for aesthetic and health purposes. Attaining more muscle mass is the ticket to increasing BMR, having the ability to eat more foods of your choice with less damage, and most importantly decreasing the risk of 30+ chronic diseases.
Anyways, if you skimmed through all of this and got to this point just remember.
Know your BMR and your TDEE (previous post)
Sleep more than 7 hours a night
Lift weights for about an hour, 2-3 times a week
…but seriously give this a read…actually the subsequent posts on those two things too. It’ll take you 5 minutes to understand the concepts that quite literally will follow you for the rest of your life.