What is Basal Metabolic Rate

What is Basal Metabolic Rate?
By Robert Adams, CPT
Head Fitness Expert

Basal Metabolic Rate (BMR) is the mimimal caloric requirement needed to sustain life in a resting individual. This is the amount of energy your body would burn if you slept all day (24 hours). This includes the body functions such as circulation, breathing, generating body heat, transmitting messages to the brain, cellular metabolism, and the production of body chemicals.

Let's look at some factors that affect BMR:

* Age: In youth, the BMR is higher; age brings less lean body mass and slows the BMR.
* Height: Tall, thin people have higher BMR's.
* Growth: Children and pregnant women have higher BMR's.
* Body Composition: The more lean tissue, the higher the BMR.
* The more fat tissue, the lower the BMR.
* Fever: Fevers can raise the BMR.
* Stress: Stress hormones can raise the BMR.
* Environmental Temperature: Both the heat and cold raise the BMR.
* Fasting/Starvation: Fasting/starvation hormones lower the BMR.
* Malnutrition: Malnutrition lowers the BMR.
* Thyroxin: The thyroid hormone thyroxin is a key BMR regulator; the more thyroxin produced, the higher the BMR.

A simple way to determine your BMR is using the basic "rule of ten". Multiply your weight by the number 10 and this is your BMR. For example a person weighing 150 pounds would have a BMR of 1500 calories. (150 x 10 = 2000).

This BMR number is about 60% of your total calorie needs for the day. The digestion and absorption of nutrients makes up 10% and the other 30% comes from your physical activity. This includes anything from blinking your eyes, getting dressed, washing the car, to running a marathon. For example, a person weighing 200 pounds would need:

Basal Metabolism…………... 60%………1500 calories
Digestion and Absorption…...10%……… 250 calories
Physical Activity…………….... 30%……… 750 calories
Energy use for the day…… 100%………2500 calories

Therefore to lose weight, one needs to consume fewer calories than are needed each day. (Your My Fresh Balance diet plan has taken your BMR into account IN ADDITION to your current normal activity level - whether you checked off sedentary or very active, etc in your preferences during setup. The caloric range you need to stay in to lose weight was given to you.)

The other, even more accurate method of calculating Basal Metabolic Rate is The Harris Benedict equation.The Harris Benedict equation is a calorie formula using the variables of height, weight, age, and gender to calculate basal metabolic rate (BMR). This is more accurate than calculating calorie needs based on total body weight alone. The only factor it omits is lean body mass and thus the ratio of muscle-to-fat a body has.

Remember, leaner bodies need more calories than less fatter ones. Therefore, this equation will be very accurate in all but the very muscular (Harris-Benedict will under-estimate calorie needs) and the very fat (Harris-Benedict will over-estimate calorie needs).

The Harris-Benedict Equation:

Males: 66 + (13.7 x W) + (5 x H) - (6.8 x A)

Females: 655 + (9.6 x W) + (1.7 x H) - (4.7 x A)

where W = actual weight in kg (weight in lb/2.2 lb/ kg)

H = height in cm (height in inches x 2.54 cm/in)

A = age in years

Ex. Joe weighs 150 lbs, stands 5'6", and is 21 years old

150 lbs/2.2 lb/kg = 68 kg

5'6" = 66 inches x 2.54 cm = 168 cm

BMR = 66 + (13.7 x 68) + (5 x 168) - (6.8 x 21)

BMR = 66 + 932 + 840 - 143 = 1695 kcals per day

Basically, you create a deficit of calories in 2 (or 3) different ways:

Eating Less Calories than you Burn each Day.
Eat anything less than what you use each day (1500 cal BMR, 250 cal digestion= 1750), consistently, and you will lose weight. So, if you eat 1200 on this day (a 550 calorie deficit), and all week long like this, you will lose 1 pound (3500 calories) in about a week.

Exercising More
Keep your caloric intake the same (1750) and create your deficit by burning extra calories. So, if you burned 500 calories through exercise alone, you will still lose 1 pound in about a week.

A Combination of Both Diet and Exercise
This is the most effective way to lose weight and keep it off.Say you cut your calories by 300 and burn 250 calories with exercise. There is your 550 calorie deficit—with much less deprivation and work.

You could speed it up by cutting more calories and exercising more—whatever works best for you. Some people hate to diet, others hate to exercise, so maybe you’ll do more or less of either one.

Of course, the example above was just for simplicity. You can cut any number of calories from your diet (more or less than the 500 in the example) and you can burn more or less than the example illustrates. As long as you are consistent, your deficit will "add up" over time…and you’ll slim down.

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