When you begin wrapping your head around the grammar of weight loss, you’ll encounter a few new, confusing terms. 

Three of the most common ones are . . . 

  • Total daily energy expenditure (TDEE)
  • Basal metabolic rate (BMR)
  • Energy balance

What do these phrases mean and how can they help you lose weight? What’s the difference between tdee vs. bmr? How does your TDEE or BMR relate to energy balance? 

You’ll learn the answers to all of these questions in this article. What’s more, you’ll also learn how to calculate your TDEE and BMR, the best equations for predicting your BMR, and more.

Let’s start by defining and demystifying TDEE.

What Is TDEE? 

TDEE stands for total daily energy expenditure, and it’s a mathematical estimate of how many total calories you burn throughout the day based on your weight, height, age, and activity level.

Once you know your TDEE, you can use this number to determine how many calories you should eat every day to lose, gain, or maintain your weight.

For example, I’m 36 years old, 6’1 and 195 pounds, and I lift weights for about 5 hours and do steady-state cardio for about 3 hours per week (I switch to high-intensity interval training when cutting), and my TDEE is about 2,800 calories.

TDEE is closely connected to the concept of energy balance, which is the relationship between the amount of energy (calories) you feed your body and the energy it expends.

If I were to eat an average of 2,800 calories per day over a period of time (typically at least a week or so), I’d be maintaining what researchers call neutral energy balance—consuming and expending the same amount of energy—and thus wouldn’t gain or lose any weight. 

Of course, some days you’ll eat more than your TDEE (positive energy balance) and other days you’ll eat less (negative energy balance), but these daily fluctuations will generally average out over time.

Once you know your TDEE, you can make effective decisions about how to eat based on three premises:

  • If you consistently eat more than that number of calories every day, you’ll gain weight.
  • If you consistently eat less every day, you’ll lose weight.
  • If you consistently eat that much, you’ll maintain your weight.

This doesn’t necessarily mean you have to count calories to lose weight, but it does mean you have to understand how calorie intake and expenditure influences your body weight and then regulate your intake according to your goals.

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What Is BMR?

Basal metabolic rate (BMR) is the average amount of calories your body requires every day to fuel essential functions like breathing, pumping blood, producing hormones, and so forth. Basically, it’s how many calories you’d burn resting for 24 hours. 

You can accurately estimate your BMR with your gender, weight, height, and age. Once you know your BMR, you can use it to determine your total daily energy expenditure (TDEE), which you can then use to create a meal plan that will help you lose, gain, or maintain your weight.

This brings us to the key difference between BMR and TDEE: 

BMR is one component of your TDEE (typically the biggest one), and thus it will always be smaller than your TDEE. For example, many people have a BMR of around 1,600 to 1,800 calories per day, and a TDEE of around 2,200 to 2,600 calories per day. Thus, your BMR will usually constitute about 70% of your TDEE.

The other three components of your TDEE are . . . 

  • The calories you burn digesting food, referred to as the thermic effect of food (TEF).
  • The calories you burn during structured exercise, sometimes referred to as exercise activity thermogenesis (EAT). 
  • The calories you burn from all other activities throughout the day, such as fidgeting, getting up and down from your chair, doing chores, and so forth, which is referred to as non-exercise activity thermogenesis (NEAT). 

Although your BMR tends to remain fairly constant, the other components of your TDEE can vary quite a bit depending on your exercise routine, diet, and lifestyle. 

For example, fidgeting can increase metabolic rate by 25-to-50%, eating a high-protein diet can increase the thermic effect of food by several hundred calories per day, and adding just a few cardio workouts to your weekly routine can help you burn an additional 1,000+ calories per week.

This is why it’s generally best to set your calorie intake based on your TDEE, which accounts for all of these factors, and not your BMR, which doesn’t.   

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How to Use Your BMR & TDEE to Lose Weight

Research shows that you must be in a calorie deficit to lose fat, but how large should that deficit be? Ten percent? Twenty percent? Larger?

In other words, should you eat 90% of your TDEE every day to lose weight? Eighty percent? Less?

One of the most common mistakes people make when trying to lose weight is overly restricting their calorie intake, what’s often referred to as “crash dieting.” Typically, this entails restricting calories to 70% or less of TDEE, or maintaining a 30+% calorie deficit. 

While this causes rapid weight loss in the short-term, it usually results in extreme hunger, binge eating, and subsequent weight gain over the long-term. 

On the other extreme, some fitness folk advocate a “slow-cutting” approach where you use a mild calorie deficit and lax workout schedule to whittle down fat stores over the course of many months. 

The advantages of this are claimed to be less muscle loss, more enjoyable workouts, and less  hunger and cravings, but this comes at a cost. Namely, slow cutting is very slow, which can feel demotivating and increase the risk of falling off the wagon. It also requires meticulous control of your calorie intake, which tends to be frustrating and unsustainable for most.

Thus, I advocate a middle road between these two extremes: maintain a moderate (but aggressive) calorie deficit of 20-to-25%. 

In other words, when you’re cutting, eat about 75% of your TDEE. For most people this works out to 10-to-12 calories per pound of body weight per day.

This formula may seem simplistic, but it tends to produce very accurate results on par with more complex equations. 

That said, if you’d like a slightly more accurate formula for estimating your BMR, TDEE, and how many calories you should eat per day to lose weight, check out the Legion TDEE Calculator, which does all of the math for you.

(And if you’d like even more specific advice about how many calories, how much of each macronutrient, and which foods you should eat to reach your health and fitness goals, take the Legion Diet Quiz.)

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What’s the Best BMR Equation?

Many people tie themselves in knots trying to figure out what the “best” equation is for estimating their BMR, but this is a waste of time. 

No BMR equations are 100% accurate for all people under all circumstances. Your lifestyle, genetics, diet, and daily habits make your actual BMR a moving target that formulas are unlikely to hit. What’s more, all of them tend to produce results that are within 100-to-200 calories of each other, which is too small of a difference to warrant splitting hairs over different formulas. 

Luckily, BMR equations don’t need to be pinpoint accurate to serve their intended purpose—they just need to be good enough so you know where to start.

Then, you can raise or lower your calories based on how your body actually responds to your diet. If you find that you aren’t losing weight as fast as you’d like, you can always subtract 100-to-200 calories from your daily calorie intake to pick up the pace. 

That being what it is, you’re probably still curious how the different BMR equations compare, so let’s quickly review their pros and cons.

One of the most commonly used BMR equations is the Mifflin-St Jeor equation, which produces very accurate results on par with other equations, but doesn’t require much math or your body fat percentage.

One catch with the Mifflin-St Jeor equation is it assumes you have a relatively normal body composition (normal musculature and 10-to-20% body fat for men and 20-to-30% for women). 

Thus, the equation can underpredict the BMR of people with above-average levels of muscle mass (especially if they also have below-average levels of body fat as well), and overpredict the BMR of people in the opposite boat.

Why not use a BMR equation that incorporates lean body mass, then, such as the Katch-McArdle equation? 

You can, but there are two reasons I usually recommend the Mifflin-St Jeor equation instead:

  1. Most people have a hard time accurately estimating their body fat percentage, and relatively small mistakes can wipe out any potential benefits of the equation. That is, if the equation is 5% more accurate, but your estimate of body fat percentage is off by 20% (relative), it’s a wash.
  2. The Mifflin-St Jeor equation is simpler and produces estimates that are almost identical to the Katch-McArdle equation for most people.

(That said, the Legion TDEE Calculator now allows you to pick what equation you use to estimate your BMR. If you feel you have an accurate grasp of your body fat percentage, go ahead and use the Katch-McArdle equation!).

The first point is self-explanatory: many people think they’re significantly leaner than they are, which translates into an overestimated BMR with the Katch-McArdle equation.

The second point requires a bit more explanation, though.

Although muscle does burn more calories than body fat, the differences are unimportant in practice.

Research shows that a pound of muscle burns around 6 calories per day (not 50, as many fitness gurus claim), and fat burns around 2 calories per day. That’s a threefold relative difference, but a trivial absolute difference that has little impact on your TDEE.

For example, I have about 40-to-50 pounds more muscle than most guys my height (6’1, 195 lb., ~10% body fat, and 36 years old), and the Mifflin-St Jeor equation pins my BMR at 1,872 calories per day. 

The Katch-McArdle equation, which accounts for my additional muscle mass and low body fat percentage, estimates my BMR is 2,089 calories per day—about 200 calories more. In the scheme of things, this is too little to matter.

It’s possible the Mifflin-St Jeor equation slightly underpredicts my energy needs, and the Katch-McArdle equation slightly overpredicts my needs. I’ll never know my true BMR with absolute certainty (even fancy devices for measuring it aren’t 100% accurate), so all that matters is that I consistently eat the same amount every day, and adjust my calorie intake as needed.

So, if you’re cutting, and a TDEE equation (which includes BMR calculation) says you should eat 2,500 calories per day to lose weight, and you aren’t losing weight, then you need to eat less, regardless of what the math says. 

Similarly, if you’re lean bulking, and a formula says you should eat 3,000 calories per day to gain weight, but you aren’t gaining weight, then you need to eat more.

And what about the Harris-Benedict equation? 

This is also a workable formula that produces results similar to the others, but most researchers consider the Mifflin-St Jeor to be slightly more accurate. There’s also the Revised Harris-Benedict equation, which is considered a smidge more accurate than the original.

Finally, I want to share one more equation with you, which is handy because of its simplicity: The Lyle McDonald resting metabolic rate (RMR) equation. Here it is: 

Male RMR: 11 x body weight in pounds

Female RMR: 10 x body weight in pounds

Yep, that’s it, regardless of your body composition. 

RMR is slightly different from BMR, but for our purposes here, they’re basically interchangeable. 

(BMR is an estimate of the minimum number of calories your body needs to sustain life, whereas RMR is the actual number of calories you burn at rest, influenced by factors like prior activity, sleep, and food intake.)

My general recommendation is to use the Mifflin-St Jeor or Katch-McArdle equation if you have a calculator to do the heavy lifting for you (like the Legion TDEE Calculator) or you want to be as precise as possible, and the Lyle McDonald equation if you want a quick and dirty solution that’s almost as accurate in practice.

All BMR equations are estimates of your actual BMR, not precise measurements. Use them to establish a starting point for your calorie intake, and then adjust up or down based on how your body responds.

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