Understanding your Basal Metabolic Rate

Your body burns calories no matter what you are doing, even while you are sleeping you are probably burning approx. 69 calories per hour, because your body uses that time to regenerate damaged tissue and build new tissue. The brain also consumes a large portion of your daily calories - even while dreaming.

So what is the basal metabolic rate? It is the amount of energy expended daily while at rest (no strenuous activity). eg. Sitting is typically 60 calories per hour, less than it takes to sleep. Assuming 552 for sleeping 8 hours and 960 calories for 16 hours of sitting, we can assume the average human uses up approx. 1512 calories per day.

Determining your basal metabolic rate (BMR) is useful when trying to lose weight. To lose weight, one must create a caloric deficit each day to eventually use up a pound worth of calories to be lose (3500) more than you are eating. It is recommended to create 5% to 10% caloric deficit each day so you can lose weight while still taking in enough vitamins for your health.

The human body is supposed to eat 1,800 to 2,000 calories per day. So if dieting you should be eating 100 or 200 calories less. So approx. between 1600 to 1800 is the ideal range for a weight loss diet. At 200 calories per day a person will lose approx. 1.7 lbs per month or 21 lbs of fat per year.

Combined with regular exercise and a person will lose weight even faster. eg. If they jog daily in addition to such a diet, enough to burn 400 calories per day, and they can lose 63 lbs of fat in a year. (Note: You can burn 400 calories by jogging for 40 minutes. And 40 minutes is only 2.8% of your day.)

Some people argue that you can crash diet by cutting your diet down to 1000 to 1500 per day, but reducing your food consumption to such a level is both dangerous and idiotic. Such a diet will also sap your mental resolve and you will probably quit the diet early and end up having your weight yo-yo up and down - which isn't going to help you at all.

When you lower your caloric intake to really low levels the basal metabolic rate will actually lower if the body enters into a starvation mode - it will begin to interfere with your mental functioning and you won't have the needed calories to be repairing the brains mental pathways (which are under a constant state of repair). Your body will begin to feast on muscle and brain tissue in order to find extra energy. The basal metabolic rate will also decrease with age, but that is a natural reflex to less calories being burned at rest, exercise and thus if becomes ever more important to be mindful of your diet as you get older.

Below is one BMR formula that I found (however I think it may be wrong, because I calculated it using my own weight, height and age and it says my BMR is 1832, which I don't think is at all accurate).

Women's BMR= 655 + (4.35 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)

Men's BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) - (6.8 x age in years)

EXAMPLE
Gary has a BMR of 1600
If he eats an average of 1800 calories per day
And he burns 500 calories per day with exercise

Then his net calorie loss should be 300 calories per day.

Gary will lose approx. 2.5 lbs per month (31 lbs per year) if he keeps it up.

There are many other formulas for calculating BMR. They are all basically inaccurate because it is really impossible to tell what each person's metabolic rate is. Each person is different. Some days are different too.

There is the Original Harris-Benedict Equation, and also the Revised Harris-Benedict Equation.

There is also the Mifflin St Jeor Equation, the Katch-McArdle Formula and the Cunningham Formula.

The formula up above is none of the five commonly used formulas. And honestly, it doesn't really matter.

I argue that people would be better off going off the average BMR, which I calculate to be approx. 1512, and then calculating their BMR based on their height and weight compared to that average, and then modified lower for age.

Thus the Moffat Formula would be:

1512 X YOUR WEIGHT / AVERAGE HUMAN WEIGHT X YOUR HEIGHT [160 lbs] / AVERAGE HUMAN HEIGHT [66 inches] X AGE MODIFIER = Your BMR

Thus using myself as an example, I am 6'2" tall and the average human is 5'6" tall, so 109.1%. Determining average weight for a human is tricky. In the USA so many people are overweight that the average has been skewed, so the "average American" is overweight. So instead I have estimated that the average healthy human weighs about 160 lbs. In which case due to my size I am 106.25%... *calculate the math*...

And my total is 1753 (minus a small age modifier). That sounds much more accurate than the sample formula from further above.

Now the trick is, how much does our metabolic rate decrease with age? Well I did find a chart for that... So I suppose it would be possible to determine what your exact rate is... but there will always be a margin for error.