BMR is the minimum energy expended by the body in order to sustain life and maintain normal bodily functions in a resting individual; i.e., this is the amount of energy a person would expend if they slept for 24 hours. BMR makes up approximately 60-70% of the calories used on a daily basis, and includes the beating of the heart, respiration and the maintenance of body temperature.
Calories consumed above your basal metabolic rate are either burned during physical activity or stored as fat. As a general rule of thumb, people with a sedentary lifestyle need a calorie intake 30% above BMR, 50% above for moderate activity, whilst heavy activity requires 90% above BMR.
Many factors can affect BMR, such as:
- Age – BMR lowers with age.
- Body composition – The more lean tissue, the higher the BMR; whilst the more fat tissue, the lower the BMR (as muscle burns more calories than fat).
- Dieting – BMR decreases whilst dieting.
- Environmental temperature – Both heat and cold raise BMR.
- Exercise – Consistent exercise can raise BMR (depending on intensity and duration).
- Gender – Men generally have a faster BMR than women.
- Growth – BMR is higher in children and pregnant women.
- Height – BMR increases with height.
- Weight – BMR increases with weight.
CALCULATIONS:
(1) General Calculation:
BMR = body weight in lb. x 10 kcal/ lb.
e.g. Julia weighs 140 lb.:
BMR = 140 x 10 kcal/ lb.
BMR = 1,400 kcal per day.
(2) Harris-Benedict Equation:
BMR Male = 66 + (13.7 x W) + (5 x H) – (6.8 x A)
BMR Female = 655 + (9.6 x W) + (1.7 x H) – (4.7 x A)
Where:
W = Weight in kg (1 kg = 2.2046 lb.).
H = Height in cm (height in inches x 2.54).
A = Age in years.
e.g. Julia weighs 140 lb., stands 5’9″, and is 23 years old.
140 lb./ 2.2046 = 63.5 kg
5’9″ = 69 x 2.54 = 175.2 cm
BMR = 655 + (9.6 x 63.5) + (1.7 x 175.2) – (4.7 x 23)
BMR = 655 + 609.6 + 297.8 – 108.1
BMR = 1,454.3 kcal per day.
TYPICAL ENERGY EXPENDITURE VALUES:
Calories burned per minute according to body weight -
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To calculate calories spent per minute of activity for your own body weight, multiply cal/ lb./ min by your exact weight, then multiply that number by the number of minutes spent in that activity.
e.g., Julia weighs 140 lb. and has spent 30 minutes walking at 3.5 miles per hour:
.035 x 140 = 4.9 calories per minute.
4.9 x 30 (minutes) = 147 calories spent.
TABLE OF LESS STRENUOUS ACTIVITY:
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