Finding Your BMR and TDEE

By
Sep 7, 2015
8020
Finding Your BMR and TDEE

I received an email this past week from a fellow paleo follower who thought he was doing everything right, and yet he was grossly overweight.  What am I doing wrong he asked?  I eat clean, I train hard and yet I look like a mini version of the Pillsbury Doughboy. What gives?  While the answer may seem obvious to most of us, based upon this email and several anecdotal stories from colleagues I’ve realized that there is still a significant gap in knowledge that needs to be addressed.  So let me put it out there for you – no matter what you eat or what diet you follow – paleo, vegetarianism, keto, etc – if YOU EAT TOO MUCH YOU WILL GET FAT.  Just the fact that you are eating ‘clean’ and healthy doesn’t mean your metabolic system can absorb and burn an unlimited amount of calories on a daily basis.  So what is that key number?  How many calories can someone eat to achieve both their dietary and body composition needs.

MEET YOUR BMR

The human body requires a significant amount of energy (i.e. calories) just to function regularly. Each day, your body must breathe, blink, circulate blood, control body temperature, grow new cells, support brain and nerve activity and contract muscles. The amount of energy (in the form of calories) that the body needs to function while resting for 24 hours is known as the basal metabolic rate, or BMR. This number of calories reflects how much energy your body requires to support vital body functions if, hypothetically, you were resting in bed for an entire day. In fact, your BMR is the single largest component (upwards of 60 percent) of your total energy burned each day.

While you can’t magically change your BMR overnight, it can be changed over time.  Knowing your personal number, how it’s calculated, and which factors most influence your metabolism, can help you use this data point to create a smarter strategy for weight loss (or maintenance).

To most accurately calculate BMR usually requires a series of laboratory measurements of carbon dioxide and oxygen analysis after a subject has fasted for 12 hours and has had eight hours of sleep. However, a rough estimation of this data is possible using the Mifflin-St. Jeor equation, a formula introduced in 1990. The Mifflin-St. Jeor equation is now considered the standard when it comes to calculating BMR.

Mifflin St. Jeor Equation

For men: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5
For women: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) – 161

While this calculation is just a rough estimate and every individual is unique – it will provide you with a good starting point for you daily needs.  

Weight and height:  What the best diet coaches around have been saying for years – to lose weight you need to gain muscle. The more mass you have and especially the more muscle mass the more fuel you need to sustain yourself on a daily basis  When you lose weight your BMR decreases and you require fewer calories per day.  

Age: As you age your metabolic rate decreases.  This is primarily due to the decline in muscle mass our across the population (approximately 5-10 percent per decade starting at age 30).  However this can be mitigated via a steady diet of weight training to help maintain and build muscle mass as you age.

Gender: Since body composition (ratios of lean muscle, bone and fat) differ between men and women, research shows a woman’s BMR is typically around five to 10 percent lower than a man’s.

A BETTER WAY

A recent newcomer to the market is a cool little device from Breezing.com that takes many of the laboratory measurements previously needed to get an accurate BMR and provides them for you on your Apple/Android device.  While it is somewhat more costly than the Mifflin St. Jeor Equation ($350 compared to free) it does promise an almost laboratory quality BMR reading – without and guesswork or formulas. 

Energy Expenditure

Once you know your BMR, you can make a more realistic guess of your total daily energy expenditure, or TDEE. This reflects the entire amount of calories, or energy, your body burns during a given day when you’re sleeping, ingesting and digesting food, working and exercising. To truly reflect the energy you’re burning, TDEE takes into account two additional aspects.

1. Thermic Effect of Activity (TEA): TEA is the total calories burned while exercising. The more intensely your muscles are working — sprinting during intervals or flexing while lifting weights — the more calories you burn. And if you’ve completed a high intensity workout, your body will have to work even harder to replenish its oxygen stores, resulting in an afterburn effect known as EPOC.

2. Thermic Effect of Feeding (TEF): When you digest food and absorb its nutrients, your body uses energy in the form of calories. While it’s only a small percentage (roughly 3 percent) of your overall daily total it’s still a critical part of the overall picture.  Missing your TDEE by just 3-5 percent could lead to a 2-5 pound weight gain in a years’ time.

Here are a couple of good online calculators to help you determine your TDEE:

http://tdeecalculator.net/

http://www.sailrabbit.com/bmr/

Conclusion

Knowing your BMR is important no matter if your goal is to lose weight, gain muscle, run harder or even taper from a training plan. It’s the first step to getting an idea of how much fuel you need to keep your engine roaring all day long. When your lifestyle/actives change or you modify your exercise routine, revisit the BMR calculator to know if you should be eating more or less. When in doubt, consult with your doctor or nutritionist to make sure you’re on the right track.

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