Weight Loss and Basal Metabolic Rate

By: 
True You
August 26, 2021

Beginning a weight loss journey can be a daunting task for many people. In addition to the basic commitment to change that is inherently required, developing a weight loss plan involves a lot of modifications to one’s diet and physical activity level. Yet while increasing physical activity level is definitely beneficial for weight loss and overall health, one of the most effective ways of losing body weight is by reducing daily caloric intake. To do this most efficiently, you’ll first want to know about your basal metabolic rate. 

What is Basal Metabolic Rate?   

Even though we think of burning calories primarily in an exercise context, the body requires constant energy for all basic functions. Basal metabolic rate (BMR) is a term that refers to the rate of energy that is expended by humans (and all endothermic animals) at rest. In other words, BMR represents the number of calories the body burns simply by being alive; this includes respiration, circulation, digestion, and the ongoing production of cells all over the body. It can also be thought of as the number of calories you would burn if you just sat in a room and didn’t move at all. 

A person’s basal metabolic rate is typically expressed as the number of calories burned per unit of time, and most of the time that means number of calories per day. Accurate determination of a person’s BMR assumes several criteria: being in a physically undisturbed state, in a setting where the body temperature can remain neutral, and not actively digesting food. For practical purposes, though, BMR is simply a figure that can help you determine the number of calories you can consume on a daily basis without gaining weight. BMR is sometimes confused with resting metabolic rate (RMR), a slightly different metric that has looser criteria for being “at rest.”  

The basic bodily functions supported by your BMR account for around 70-75% of calories burned every day. How many calories you burn by default is affected by many different factors, including sex, height, weight, age, and genetic background. However, the most significant individual factor in BMR is the amount of non-fat tissue in your body. So, for example, two people who weigh the same amount would have different BMRs if one of the people had more muscle on their body. This is because the cells that make up muscle require more energy to function than fat.  

How is Basal Metabolic Rate Calculated?

In order to make the best use of BMR in the context of your weight loss goals, you first need to be able to calculate it. The most accurate way of determining BMR is by participating in a special lab test that uses either direct or indirect calorimetry; this process determines the precise amount of energy expended in a reaction by measuring either the amount of heat produced or the exchange of gasses. This is typically achieved by breathing into a special device called a calorimeter. 

Since the lab test option isn’t cost effective or convenient for most people (you usually have to stay overnight in a lab environment to get maximum accuracy), there are a series of equations that can be used to estimate or predict basal metabolic rate. The very first test, called the Harris-Benedict equation, was developed over a century ago but was then updated in the 80s. Then, in the 90s, a new model called the Mifflin-St Jeor equation was introduced and was found to be significantly more accurate. Fortunately, there are a number of BMR calculator options that make it easy to find your personal BMR. 

How Can Knowing My BMR Help With Weight Loss?  

The main purpose of determining your basal metabolic rate is to be able to adjust your diet plan accordingly. With your BMR in hand, you’ll know the minimum daily calories needed to keep your body functioning, and this amount can act as a guide for planning meals and general calorie intake. To really get the benefit of knowing your BMR, though, it needs to be combined with information about how much physical activity you do each day. This figure is known as total daily energy expenditure (TDEE), and it is calculated by multiplying BMR by an estimated level of physical activity: 

  • Sedentary (little or no exercise, desk job): TDEE = BMR x 1.2 
  • Light (light exercise 1-3 days a week): TDEE = BMR x 1.375
  • Moderate (moderate exercise 3-5 days a week): TDEE = BMR x 1.55
  • Heavy (vigorous exercise 6-7 days a week): TDEE = BMR x 1.725
  • Athlete (regular daily training): TDEE = BMR x 1.9 

As an example, consider a 45-year-old male who is 5’8” tall and weighs 200 pounds; using the Mifflin-St Jeor equation noted above, this man’s BMR would be about 1750 calories per day. Assuming he led a relatively sedentary lifestyle, we can calculate his total daily energy expenditure as 1750 x 1.2 = 2100. If he raised his activity level from sedentary to some light exercise a few days a week, his adjusted BMR would be 1750 x 1.375 = 2406. This means that even a marginal increase in physical activity can make a significant difference in the amount of calories burned every day. 

The implications for weight loss are related to a fundamental truth about calorie intake: if you consume more calories than your body needs, you will gain weight, and if you consume fewer calories than your body needs, you’ll be in a calorie deficit and lose weight. So, once you know your BMR, you have a variety of different ways to modify your weight loss plan. For example, if cutting calories dramatically seems too challenging, you could increase your daily physical activity. Or, if adding in an elaborate exercise plan isn’t currently feasible, you can lose weight simply by reducing calories to below your TDEE value. 

Additional Considerations      

While the calculations mentioned above are a great way to get a big picture perspective on your daily energy needs vs energy intake, there are additional factors that can make weight loss more efficient. One of the most significant contributors to your body’s ability to burn fat is the proportion of muscle mass in your body. Muscle has much higher caloric needs than body fat or other tissue, so if you build muscle, that is a direct way to increase BMR and thereby increase the number of calories you can consume in a day before weight gain occurs. 

Another important part of using BMR to help you lose weight is calorie tracking. If you’ve ever tried to record a daily food log, you know how quickly those calories can add up—even when it doesn’t seem like you’ve eaten that much. For many Americans, snack items, soft drinks, and fast food are a surprisingly large part of a diet. But it’s only when you start tracking what you eat on a daily basis that you can really begin to control your eating habits. These days, consumers are fortunate to have numerous apps and websites that can help you keep track. 

Freedom is Waiting

If all this focus on calories and calculations seems like a bit too much to handle, you’re not alone. While the traditional way of thinking about weight loss can work for some people, many find it overwhelming and hard to adjust to. That’s why True You Weight Loss offers a totally different approach through non-surgical weight loss procedures. Rather than going back, yet again, to another weight loss plan, you can finally gain control of your weight loss journey. If you’d like to learn more about how you can find this kind of freedom, contact us today to request a consultation

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