Why Basal Metabolic Rate Matters to Your Weight

by Andrea Dietrich, B.Kin., CSEP-CPT

Fitness and Training Coordinator, Recreation Services at the University of Manitoba

What is it Basal Metabolic Rate?

Basal metabolic rate, or BMR, is the bare minimum amount of energy expended by an individual at rest while awake. More precisely, the amount of energy your body needs to breathe, lay restfully awake, and control body temperature. Ideally, you would have fasted for 12 hours, and the environment was temperature-controlled as well.

So how do you actually use this information? Let’s change the word energy to the word calories. BMR is then the bare minimum amount of calories your body needs to merely function. This has implications for your diet, whether you are trying to lose, gain or maintain weight, feed growing muscles, or spend your weekend lying in bed in a dark room, quietly just existing.

Most of us do more (much more) than lay in bed on an average day, and even tasks like sitting up, eating and digesting, and walking to the mailbox consume calories. We call this your total daily energy expenditure (TDEE), and it is your BMR plus the number of calories burned throughout the day. That is why we generally need to eat more to support our everyday activities. However, if we begin eating more calories than we are regularly burning, that is when we start to notice weight gain. 

This is not to say that eating fewer calories than your predicted basal metabolic rate is recommended for weight loss, in fact, we highly discourage it. If your body cannot function on a basic level, you may encounter all sorts of health issues, some of which are irreversible. Loss of body temperature control, wasting of muscle mass, and loss of bone mass are just to name a few.

How to Calculate BMR and How to Use It

When it comes to basal metabolic rate, everyone is just a little bit different. We base your BMR on biometrics such as your height, weight, age, and gender, so it is unlikely that your BMR will be the same as that of your friend or loved one.

We recommend trying Active.com’s BMR calculator to determine your own. Using a similar calculator, you can also assess your predicted total daily energy expenditure based on your activity level.

Now let us say your BMR was 1200 calories and day and your TDEE was 2100 calories a day. If you are attempting to lose weight, we would recommend you eat between 1200 and 2100 calories a day. If you were trying to maintain your current weight, we would recommend eating about 2100 calories a day, and if you were trying to gain weight, we would recommend eating over 2100 calories a day. As an aside, it does matter the quality of the food in which the calories are coming from. 200 calories of fruit and vegetables are far more nutritious than 200 calories of potato chips.

How to Increase Your BMR and Why

As you can imagine, having a higher BMR is preferred to burn more calories just by breathing, but most people are not so lucky. We say lucky, because BMR is, for the most part, determined by genetics. Sorry. However, there are a few things you can do to give your metabolism some help. 

Muscle tends to burn more calories on average than fat, so reducing your fat mass and increasing your muscle mass will have the effect of increasing your BMR. The good news is, to improve muscle mass and decrease fat mass, we recommend exercise, and the act of exercising also burns calories! You get two birds with one stone or a handful more of strawberries with one more lap around the track as it were. There are some myths out there and some less effective ways to try and increase your metabolism; however, exercise, especially resistance training, has been proven to be the most useful in this area.

If you are considering spending the weekend lying in bed in a dark room, quietly just existing, may we suggest one of our fantastic group fitness classes instead? We modify most of our fitness classes to meet all fitness levels, and our qualified staff are happy to help anyone new to the class. You can even wear your pyjamas, provided they are clean.

Henry, C. (2005). Basal metabolic rate studies in humans: Measurement and development of new equations. Public Health Nutrition,8(7a), 1133-1152. doi:10.1079/PHN2005801

Johnstone, A.M., Murison, S.D., Duncan, J.S., Rance, K.A., Speakman, J.R. (2005). Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine, The American Journal of Clinical Nutrition, Volume 82, Issue 5, 1 November 2005, Pages 941–948, https://doi.org/10.1093/ajcn/82.5.941