If you set out to lose weight or maintain a target weight as an athlete or fitness or bodybuilding enthusiast, your coach or physician will often tell you that you need to estimate your BMR and TDEE and to set daily calorie intake limits based on the energy requirements calculated from these measures. Hence, it can be beneficial to understand the **meaning, assumptions, and limitations of both BMR and TDEE, **as well as **what differentiates one from the other when used in weight management, be it weight loss or weight gain.**

## TDEE and BMR – Short Comparison

TDEE stands for “Total Daily Energy Expenditure”, and is synonymous with EER or “Estimated Energy Requirement” to maintain your current weight. BMR stands for Basal Metabolic Rate, sometimes mistakenly called “base metabolic rate” or even “basic metabolic rate”.

**BMR **is the daily energy required to keep your body alive in an awake resting state, under strict conditions as described in detail below. Think of it as the Calories your body would need if you were restricted to lying down awake all day. As such, BMR is a component of TDEE since **TDEE **is simply BMR plus any energy used in your daily physical activities which include voluntary ones such as walking, climbing stairs, sitting, speaking, working, training and exercise, sports activities, weight lifting, etc. and involuntary ones such as the thermic effect of food digestion and involuntary muscle contractions.

In light of maintaining an energy balance and controlling your caloric intake for the purpose of weight loss, weight gain, or maintaining a given body weight, TDEE compares to BMR in the following ways:

Characteristic | TDEE | BMR |
---|---|---|

What it measures | Total energy required daily to maintain energy balance. Includes BMR, the thermic effect of food, energy spent on non-exercise and exercise activity | Just the bare minimum energy needed to keep you alive and awake. It does not include any activity other than lying flat, not even digestion. |

Measurement units | Typically measured in Calories or kilocalories per day | Typically Calories or kilocalories per day. Sometimes calculated in kcal·m^{-2}·h^{-1} – kilocalories per body surface area per day. |

How is it calculated? | Estimated from BMR multiplied by an activity level multiplier | Measured in laboratory conditions, but more often estimated through regression equations based on height, weight, age, and sex. |

Common usage in weight loss | To inform dietary limits based on the estimated daily caloric needs and weight goals. | To set a baseline for dietary restrictions. Going below BMR for any length of time equals starvation. |

Effect of frequency and intensity of exercise | Significant | None by design |

You should find that most of the time you would only find yourself needing to calculate BMR if you want to apply a custom physical activity multiplier in your energy requirement calculations. Otherwise, any TDEE calculator will simply first estimate your BMR, then multiply it by an activity level multiplier based on your chosen level of typical physical activity.

## What is BMR And When Would You Need It

BMR, or Basal Metabolic Rate, is very strictly defined in the medical literature used by sports physicians, nutritionists, coaches, and professional athletes. It is measured in laboratory conditions, defined as such ^{[1]}:

- The subject should be completely rested, both before and during the measurements. They should be lying down and fully awake.
- The subjects should be fasted for at least 10 –12 hours before the measurements are taken.
- The environment in which the measurements are taken should be thermo-neutral (22–26°C) so that there is no thermoregulatory effect on heat production.
- The subject should be free from emotional stress and familiar with the apparatus used.

Under these conditions, a minimum rate of heat production free of the effects of any consumption of food and ‘extreme’ physical environments is measured using **open circuit calorimetry**. The result is in energy units, typically MJ (Megajoules), which are then converted to the more familiar calories, kilocalories, and Calories (1 Calorie = 1 kilocalorie).

As you can see, **accurately measuring BMR is not something you can do outside of a laboratory.** Therefore, for everyday purposes, BMR calculations are performed using one of several regression equations developed by studying many subjects in laboratory conditions and establishing the relationship between their height, weight (BMI), age, and biological sex. Some equations use body surface area as well, but it is yet another estimate so these are typically less accurate.

Our BMR calculator uses one such formula which has shown good validity, the Mifflin-St Jeor formula ^{[2]}, which was found by the American Dietetic Association to be the most practically reliable ^{[3]}. Regardless of how it is estimated, BMR tends to decrease with age and is, on average, lower in women as compared to men:

Ultimately, you would only need to calculate your BMR if you want to find out your daily energy requirement estimate on your own, or if you want to manually calculate your TDEE from BMR.

## Assumptions, Limitations, and Accuracy of BMR Calculations

The BMR calculations performed by most calculators suffer from the limitations of the methods used to arrive at the equations they rely on. For example, some previously well-regarded formulas have been found to suffer from significant bias when applied to a variety of situations:

“…in most cases the current FAO/WHO/UNU predictive equations overestimate BMR in many communities. The FAO/WHO/UNU equations to predict BMR were developed using a database that contained a disproportionate number – 3388 out of 7173 (47%) – of Italian subjects. The Schofield database contained relatively few subjects from the tropical region”

Henry CJK, (2005) “Basal metabolic rate studies in humans: Measurement and development of new equations.”

Ideally, you should be aware of the formula used and how it has been derived, and be aware of biases that might apply to your specific scenario.

Even with the best formula applied, a BMR calculation produces merely an estimate, and it comes with known error bounds, typically a few percent, but sometimes more. Like any other average, it suffers from issues when applied to an individual which is why it is of utmost importance that you **understand your specific circumstances, monitor your physical state, and consult a physician or another health professional before making any significant changes to your diet, lifestyle, and others that may affect your health**.

## What is TDEE and How it Differs from BMR

TDEE, an abbreviation of Total Daily Energy Expenditure, is the total amount of energy you need to maintain your body’s energy balance. In other words, it is the amount of Calories you need to consume to maintain your body weight. Since it is calculated as a product of the Basal Metabolic Rate, it is also measured in energy units such as Joules and Megajoules, which can also be expressed as calories, kilocalories, and the Calories used predominantly in sports and nutrition books.

### How to Calculate TDEE

It is not possible to measure TDEE outside of a lab (with even that being a challenge), so most often the daily energy requirement is estimated from BMR multiplied by a physical activity level multiplier.

**Typical BMR multipliers for TDEE** calculation are:

- Sedentary: 1.2 x BMR
- Light: 1.375 x BMR
- Moderate: 1.55 x BMR
- High: 1.725 x BMR
- Extreme: 1.9 x BMR

For example, weightlifters training 6-7 times a week would fall into the “High” category. If you are mostly doing cardio a couple of times a week, then “Light” is likely right for you, assuming that is your main physical activity. See some activities with a high calorie burn.

### Difference Between TDEE and BMR

The above makes it obvious that **the main difference between TDEE and BMR is that the former includes energy expended on all kinds of physical activity, whereas the latter is designed to exclude it**.

More specifically, TDEE includes, on top of BMR:

- TEF, the thermic effect of food
- NEAT, non-exercise activity thermogenesis
- EAT, exercise activity thermogenesis

It is evident that for weight loss specifically, or weight management in general, TDEE is a more appropriate starting point than BMR since it relates to how one spends their typical day whereas BMR is more of a clinical measure.

## Accuracy and Limitations of TDEE Estimations

The assumptions, limitations, and inaccuracies inherent to BMR calculations translate fully to TDEE, as the latter is a derivative of the former. On top of that, TDEE adds another source of error and uncertainty which is the physical activity level. Arguably, the multipliers used and the descriptions of these physical activity levels are only ballpark numbers, so no matter how accurate your BMR estimate is, even if it is derived by open circuit calorimetry, the TDEE estimated from it may be significantly off if the physical activity is more or less energy intensive than the multiplier implies.

Therefore, you should always interpret any TDEE calculation as presenting you with nothing more than a **rough guideline**. Monitoring your average weight loss or gain, or daily weight change, is a good way to ensure you are not over or under-eating. As always, it is recommended to consult with a health professional before undertaking health-related changes to your diet or lifestyle.

## How to Use TDEE for Weight Management

Body weight management, more often weight loss, but sometimes weight gain for fitness / bodybuilding practitioners, can be helped by TDEE when used under the caveats discussed above, but this is a tricky matter. Typically, a coach would recommend either:

- increasing your physical activity so as to increase TDEE, while maintaining your current caloric intake
- or decreasing your daily calorie intake so it is some percentage of TDEE below 100%, e.g. 80-90% or a fixed number of Calories such as 500 Calories per day

However, these methods may be seen as obsolete with recent scientific advancements in management of body weight through adjustments in daily caloric intake. Basically, the interplay between TEF, NEAT, and exercise activity is too complex for simple rules such as the 500 Calories per day or 3500 kcal per week rules to work well for most ^{[4][5]}. For an in-depth exploration of the topic, see The Mathematics of Weight Loss – Putting the 3500 Calorie Myth to Rest.

Our Weight loss calculator makes use of these and can be used to assist in more accurate calorie calculations for losing weight, and also contains an example calorie deficit curve.

## A Recap on TDEE vs BMR

BMR differs from TDEE mainly in that it does not incorporate any energy expended on physical activity by design, including the thermic effect of food. TDEE, on the other hand, includes all of your daily activities, including fitness exercises, bodybuilding, lifting, running, and so on. Therefore, it is not as much TDEE vs BMR, but rather BMR used to calculate TDEE which can be used to inform your caloric intake and dietary plan.

For example, if one has a TDEE of 2,300 Calories, they would aim to achieve a certain caloric deficit of say 500 Calories per day, thus limiting their daily food intake to roughly 1,800 Calories.

However, in more recent days the science of body weight management has advanced significantly, so no matter if weight loss or weight gain is your goal, you are better off relying on equations designed specifically with that goal in mind as suggested in the previous section instead of simple rules of thumb for reducing your energy intake by a specific number of Calories.

*Importantly, TDEE and BMR calculations are not by themselves to be treated as recommendations for change of diet or adjustments to physical activity and training regimens. It is always recommended that you consult a physician or another specialist before embarking on a weight loss journey, or if you need to maintain or gain weight for any purpose.*

#### References:

[1] Henry CJK, (2005) “Basal metabolic rate studies in humans: Measurement and development of new equations.”, *Public health nutrition.* 8:1133-52.

[2] Mifflin. A.D., St Jeof. S.T. (1984) “A new predictive equation for resting energy expenditure in healthy individuals”, *The American Journal of Clinical Nutrition* 50 (2), 241-47; DOI: 10.1093/ajcn/51.2.241.

[3] Frankenfield M.S., Roth-Yousey. L., Compher. C. (2005) “Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Nonobese and Obese Adults: A Systematic Review”, *Journal of the Academy of Nutrition and Dietetics*, 105 (5), 775-789; DOI: 10.1016/j.jada.2005.02.005

[4] Hall K.D. et al. (2011) “Quantification of the effect of energy imbalance on bodyweight”, *Lancet (London, England)* 378(9793):826-37; DOI: 10.1016/S0140-6736(11)60812-X

[5] Hall K.D. (2008) “What is the required energy deficit per unit weight loss?”, *International Journal of Obesity* 32, 573–576; DOI: 10.1038/sj.ijo.0803720

An applied statistician, data analyst, and optimizer by calling, Georgi has expertise in web analytics, statistics, design of experiments, and business risk management. He covers a variety of topics where mathematical models and statistics are useful. Georgi is also the author of “Statistical Methods in Online A/B Testing”.