Metabolism and Metabolic Rate


Do you know what your metabolism is? Many people think it’s just to do with weight gain or weight loss, but it is far more complex than that. The dictionary meaning is,

“Your metabolism is the way that chemical processes in your body cause food to be used in an efficient way, for example to make new cells and to give you energy.” – Collins Dictionary

What many people don’t realize is that the body burns calories even when it is resting. The body doesn’t just burn calories when performing rigorous physical training. Our body requires calories to produce energy for many body processes.

Your body constantly needs energy just to stay alive. The problem is, many people take in more calories than their body needs for fuel or energy, which raises a very good question.

How do you know how much energy your body needs every day for good health? This is vital for weight management, as ingested calories which are excess to energy requirements will very likely be stored as body fat.

Basal Metabolic Rate (BMR)

BMR or Basal Metabolic Rate refers to the amount of energy needed by the body while it is at a resting state. When the body is at rest, it is still burning energy, as it performs the vital processes to keep us alive, such as breathing, the heart keeping beating, brain function, and more.

For most people, the Basal Metabolic Rate, or the calories that the body needs for automatic functioning, is what comprises the largest amount – more than 60% – of total energy that the body burns every single day.

Measuring BMR

The BMR is measured during the post-absorptive state, which means the digestive system is at rest. Therefore, if you want to determine your BMR, your body has to undergo at least 12 hours of fasting prior to testing.

Most experts use a formula called the Mifflin-St. Jeor equation to determine an individual’s BMR. However, others prefer to use the Harris-Benedict equation, although the first is considered more accurate than the latter. It is for this reason that the Mifflin-St. Jeor is now deemed to be the standard BMR calculator.

Formula for Calculating BMR

If you’re interested in calculating your BMR, here are the 2 different types of formulas for making the calculations.

For Men

The Mifflin St. Jeor Equation
BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5

The Harris Benedict Equation
BMR = (13.75 x Weight in kg) + (5 x Height in cm) – (6.76 x Age) + 66

For Women

The Mifflin St. Jeor Equation
BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) – 161

The Harris Benedict Equation
BMR = (9.56 x Weight in kg) + (1.85 x Height in cm) – (4.68 x Age) + 655

Factors to Consider in Calculating Your BMR

Age

An individual’s metabolic rate may tend to decrease with age. It is because as we age our muscle mass declines, as much as 5-10% every ten years starting at age 30. However, this decline in muscle mass can be prevented or at least reduced through strength training.

Gender

Gender is another important factor, as men and women differ in ratios of muscle, fat and bone mass. Studies reveal that a man’s BMR is higher than a woman’s, as much as 12%. Research also shows that the BMR of a woman changes before and after her menstrual cycle.

Weight and Height

The heavier you are, the more energy your body needs in order to fuel itself at a maintenance level. If you lose weight, your Basal Metabolic Rate will reduce as your body requirements will become less.

Body Temperature

An increase in body temperature causes an increase in Basal Metabolic Rate. This means that if a patient has a fever, their BMR is also higher.

Stress

Stress causes the body to produce higher amounts of norepinephrine and epinephrine hormones which results in a faster heart rate and increased respiratory rate. In turn, the body experiences an increased metabolic rate to compensate for changes in bodily functions.

Caffeine Intake

Studies have also shown that consuming 5 to 100 milligrams of coffee on a daily basis may cause an increase in basal metabolic rate, up to 7%. The same thing is also true for those who smoke.

Every person has a huge potential control over their energy or calorie usage. While you may not be able to control how many calories your body needs to keep your blood circulating or your heart beating, you can certainly burn excess calories just by exercising and eating healthy foods.

Making little changes to your daily activities can influence your body’s metabolic rate, which will help use more energy even while resting.

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