Calculation of The Basal Metabolic Rate

Basal Metabolic Rate is the number of calories required to keep your body functioning. It is known also as Metabolism, there are many factors that affect the calculation of the BMR or metabolism. Such factors are Body Composition / body size, gender, age, ambient temperature, starvation, health condition, and hormones.

Body Composition / Body size is affecting the BMR because body composition: has to do with the fat tissue and muscles as well as water amount in the body. For instance, fat tissue has a lower metabolic activity than muscle tissue. Furthermore, as lean muscle mass increases, metabolic rate increases. Also, metabolic rate increases as weight, height, and surface area increase.

Gender affects the BMR, because, the basal metabolic rate (BMR) among women is lower with 5 to 10 percent than in men. This is because women usually possess more body fat tissue and less muscle mass than men of similar size.

Age affects the BMR, because: Insofar as we get older especially after the age of 30 the lean muscles decrease which can result in declining with 0 3 percent per year in BMR.

Ambient temperature affects the BMR: Climate and body temperature also play role in the metabolism, for instance, the BMR of people who live in tropical climates is generally 5 to 20 % higher than those who live in hot climate areas, because the coldness takes energy from the body. The bodywork against the coldness in order to keep the body warm.

Starvation affects the BMR because starvation lowers the BMR.

Health condition affects the BMR: For instance, fever, illness, or injury may increase the resting metabolic rate.

Hormones: Hormones are also affecting the BMR, (adrenalin) and (noradrenaline). Also, hormonal levels of the Thyroxine (T4), which released by the thyroid glands. This hormone has a significant effect on metabolic rate.

An example of calculating BMR using the metric system for the formula:

• Gender = Male

• Age = 40 years

• Height = 185 cm

• Weight = 75 kg

• Now i apply the information to the formula.

BMR = (88.3 + (13.4 x 75) + (4.8 x 185) – (5.7 x 40))

BMR = 1753.3 Calories / 24 hours

Now, i can multiply the BMR by the activity factor (x1.375) to calculate the calories that i need to maintain my weight:

Calories needed to maintain my weight = 1753 x 1.375 = 2410 calories.

Typical values of Physical Activity Level (PAL)

The following examples give an indication of the range of values of PAL.

Good to know these also for later calculation.

Units of energy

• 1 kilo Joule (kJ) = 0.24 kilocalories (kcal)

• 1 kcal = 4.17 kJ

• 1000 kJ = 1 Mega Joule (MJ)

So much energy gives 1g of each energy sensor:

• Protein = 17 kJ eller 4 kcal

• Carbohydrate = 17 kJ eller 4 kcal

• Fat = 37 kJ eller 9 kcal

• Alcohol = 29 kJ eller 7 kcal

Work done = force x distance (W= F xs)

Power = Work done/time ( P=W/t)  where P is power, W is work, and t is time.