Basal betabolic rate (biochemistry) Slmch

1. BASAL METABOLIC RATE
- JASSIM

2. Definition
Requirement of BMR
Calculation of BMR
Normal values
Factors affecting BMR
Significance of BMR
CONTENTS
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3. Introduction
Basal metabolic rate is defined as
the minimum energy required by
a person at complete physical
,mental,digestive rest.

4. Requirement of BMR
BMR is the minimum amount of energy required
to carry out basal vital body functions like
respiration, heart rate, circulation, renal functions,
brain functions, conduction of nerve impulse and
transport across membrane etc.

5. Calculation of BMR
BMR is measure using Benedict's-Roth apparatus
Procedure: The subject breathes in oxygen for 6
minutes. Let the volume be Y liters. Calorific value of
O, is 4.8 Kcal/liter. So, Heat produced in 6 minutes =
4.8 x Y Kcal
Heat produced in a hour = 4.8 Y X 10 Kcal.
BMR=(4.8 X Y X 10 Kcal)/A , where A is surface area in
sqm

6. Normal values
BMR is expressed in Kcal/square meter body surface area/hour
(i.e. Kcal/sq.m/hr).
Adult male= 35-38 Kcal/square meter body surface area/hour.
Adult female =32-35 Kcal/square meter body surface
area/hour.
Children =53 Kcal/square meter body surface area/hour.

7. Factors affecting BMR
1) Surface area: BMR is directly proportional to the body
surface area. Higher the body surface area, higher is the
BMR.
2) Age: BMR is higher in infants and young children as
compared to adults. BMR is at its highest during the first 5
years of age and then gradually decreases.
3) Gender: Males have higher BMR than females.

8. 4) Climate: BMR is higher in cold climates compared to warm
climates
5) Starvation: BMR decreases during starvation.
6) Exercise: BMR increases during exercise.
7) Fever: BMR increases during fever. (10- 12% increase is
noted per degree centigrade rise in body temperature).
8) Hormones: Thyroxine increases BMR. So BMR increases in
hyperthyroidism and decreases in hypothyroidism.

9. Significance of BMR
1) Planning balanced diet:
Determination of BMR is important in calculating
energy requirement by a person and planning a balanced
diet.
2) Diagnosis of thyroid hormone disorders:
In hypothyrodism BMR decreases (up to 40%
decrease). In hyperthyroidism, BMR increases (up to 70%
increase).

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