## What is BMR (Basal Metabolic Rate)?

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. You can use IIFYM’s BMR calculator to find your BMR.

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 you were resting for an entire day. It may surprise you to know that your BMR is the single largest component (more than 60 percent) of your total energy burned every day.

While you can’t magically change your BMR right away, knowing your personal number, how it’s calculated, and which factors most influence your metabolism, can help you use your BMR to create a smarter strategy for weight loss (or maintenance).

### What is TDEE (Total Daily Energy Expenditure)?

Your total daily energy expenditure (TDEE) is the total number of calories you burn each day. To prevent weight gain, calorie intake (energy intake) must be balanced with energy expenditure. You can use IIFYM’s TDEE calculator to find your TDEE.

You need to understand how your body creates energy in order to understand what energy expenditure is. Your body creates energy in the form of heat to provide fuel for movement and daily functions.

The energy found in food is measured in **kilocalories** or calories. A kilocalorie is the amount of heat required to raise the temperature of one kilogram of water one degree Celsius. The total number of calories you burn for energy each day is your **total daily energy expenditure** or TDEE.

Total daily energy expenditure can vary from person to person depending on body size, gender, body composition, genetics, and activity level. The total energy expenditure for a small, sedentary woman may be 1800 calories or less per day. But the TDEE for a large man may be 2000 calories or more.

### BMR, TDEE and Weight Loss

- With the definitions about, it’s easy to see that BMR is a subset of TDEE. Your TDEE is your BMR plus whatever energy you expend during exercise or other activities that burn calories.
- TDEE is the most important bit of information available to us when trying to gain muscle or burn fat and lose weight, because it represents the total number of calories we burn.
- To burn fat, we must eat less calories than our TDEE which will force your body to use your stored body fat as fuel, but not less than our BMR which we need to function properly.
- This is why when counting macros, we always base our calorie intake on our TDEE calculator numbers, and not BMR, like so many misinformed coaches do.

### How do I calculate my 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 you were resting for an entire day. It may surprise you to know that your BMR is the single largest component (more than 60 percent) of your total energy burned every day day.

While you can’t magically change your BMR right away, knowing your personal number, how it’s calculated, and which factors most influence your metabolism, can help you use your BMR to create a smarter strategy for weight loss (or maintenance).

**You can use the IIFYM BMR calculator to measure your BMR**

### BMR: Your Basic Burn

To most accurately calculate BMR, an expert takes 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. Since it’s proven to be more accurate than previous BMR formulas, the Mifflin-St. Jeor equation is now considered the standard when it comes to calculating BMR.

#### The 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

You’ll can use your BMR as a rough estimate to set your basic needs. This doesn’t vary too much for a male or female of the same age and body weight. However, we do need to take into consideration weight, height, age and gender.

#### Weight and height:

The more mass you have, the more fuel you need to sustain larger organs. This is why heavier and taller people have a higher BMR. When you lose weight, your BMR decreases and you require fewer calories a day. In contrast, when you gain dense, heavier muscle, your BMR increases.

#### Age:

Metabolic rate decreases as you age because muscle mass declines by five to 10 percent each decade after the age of 30. However, weight training can mitigate that loss in muscle mass. Circuit training that incorporates full-body resistance exercises (like squats, lunges and core work on a balance ball) is great for this. Strength training individual muscle groups in isolation isn’t as effective in strengthening your body for daily movement that always incorporates a mix of muscle groups.

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.