biochem

2. DIET & NUTRITION
• Caloric value is defined as the amount of heat energy obtained by burning 1 gm
of food stuff completely in the presence of O2.
• In vitro caloric value of different foodstuffs is determined in a special apparatus
called BOMB CALORIMETER.
PROCEDURE & PRINCIPLE:-
1. A weighed amount of the sample is burnt in an atmosphere of O2 by an
electrically heated platinum wire.
2. The heat evolved is absorbed in a weighed amount of water which surrounds the
burning chamber.
3. Rise of temperature is recorded with the help of sensitive thermometer.
• Unit of energy:- The unit of energy is calorie (c) .
• What is CALORIE ? is defined as amount of heat required to raise the
temperature of 1 gm of water by 1C◦( specifically from 15 C
◦
to 16 C)
• KILOCALORIE:- is a unit thousand times of the ordinary calorie. Kilocalorie
ic Calorie with capital C.Calorie usually means kilocalorie.
• AVERAGE ENERGY VALUE
• Carbohydrates:- 4.1
• Fats:- 9.3
• Proteins:- 4.1

3. • Metabolic rate:- out put of energy by a person which is expressed
as kcals/sq meter body surface area/hr.
• Basal metabolic rate(BMR):-Defined as the amount of heat given out by a
subject under basal condition and is expressed as kcals/square meter surface area
of the body /hour under basal conditions.
• The Basal conditions
1. Person should be awake, at complete rest both physical & mental.
2. Person should be in overnight fast (post absorptive state)
3. Should be in recumbent /reclining position in bed
4. There should be normal environment, normal temperature & pressure
Normal BMR values
• Adult males =40C/sqm/hr
• Adult female =37C/sqm/hr
Factor influencing BMR
 Age, sex & climate
 Surface area
 Racial variation
 State of nutrition
 Body temperature
 Barometric pressure
 Habits & drugs
 Various hormones
 BMR calculation by Harris method
BMR (Men)=66+(13.7×W)+(5×H)- =6.8×A
BMR (women)=55+(9.5xW)+(1.8xH)-(4.7xA)
 BMR by Read’s formula:-
BMR=0.75 (PR+ 0.74x PP) -72

4. BMR / BEE
BMR calculation requires : surface area , RQ & O2 consumption / L
1. Du Bois’ surface area formula:
A=H0.725×W0.425×71.84
Where,
A= Surface area in sq.cm
H= Height in cm
W= Weight in Kg.
A (in sq. meter) = H0725×W0.25×0.007184
2. Surface area is also calculated by using Nomogram.
• A BMR between -15 to +20% is considered normal.
Present deviation of BMr
difference between actual & standard BMR
=___________________________________ x 100
standard BMR for particular age & sex

5. Increased BMR
 Fever : infections and febrile diseases
 Thyrotoxicosis
 Leukaemias & polysythemia
 Hyperthyroidism & cushing diseases
Decreased BMR
 Myxoedema
 Addison disease
 During sleep
Importance of BMR
1. As a diagnostic aid
2. For calculation of caloric requirements
3. To find out Effect of food and drugs.

6. Respiratory Quotient (RQ)
• RQ is the ratio of the volume of CO2 produced by the
volume of O2 consumed(CO2/O2),during a given time.
• A Normal RQ in a healthy adult over mixed diet =0.85
• FACTORS AFFECTIN RQ:-
1. nature of diet
CHO=RQ 1
Fats= RQ 0.7
proteins=RQ 0.8
2. Interconversions in body
3. Muscular exercise
4. Starvation
RQ is increased in acidosis, febrile conditions.
RQ is decreased in alkalosis, advanced D.M.
IMPORTANCE OF RQ
1. a guide as to the type of food burning
2. helpful in determining metabolic rate
3. helps in diagnosis of various diseases
CALORIC REQUIREMENT depends upon
1. BMR
2. Specific dynamic action (SDA)
3. Physical activity
Kcals/LO2 at RQ values.
Kcal/L
O2
RQ
4.689
0.71
4.739
0.75
4.801
0.80
4.825
0.82
4.862
0.85
5.047
1.00

7. Energy expenditure/hr of 70 Kg person
84 kcals
Lying still and awake
100 kcals
Sitting at rest
120 kcals
Standing still
192 kcals
Walking slowly (I mile/hour)
348 kcals
Walking moderately fast (4 miles/hour)
500 kcals
Swimming
650 kcals
Walking very fast
1100 kcals
Walking upstairs

8. Total calorie requirements/24 hrs
MEN: Calories
Shoe maker (sedentary) 2000-2400
Carpenter (light work) 2700-3200
Farmer (moderate work) 3200-4000
Labourer (heavy work) 4000 or more
WOMEN:
House wife 2300-2900
Seamstress( needle) 1800-2100
Seamstress (machine) 2300-2900
Infants up to 6 months 110-120
Infants up to 1 yr. 115-150
Children 1-10 yrs. 115-2000
Boys 10-18 yrs. 2500-3000
Girls 10-18 yrs. 2250-2300

9. Standard BMR values (kcals/sq.meter/hr)
BMR
Male Female
Age
(years)
53.0 53.0
01
49.3 48.4
05
44.0 42.5
10
38.6 35.3
20
36.3 34.9
40
34.9 32.7
60

10. SOME TERMINOLOGIES
• Resting Metabolic Energy (RME)
It is energy expenditure measured in individuals at rest without food for 2 hrs.
It is 10 % greater than BMR.
• Minimum Metabolic Rate
It is minimum metabolic rate during sleep / starvation.
• Maximum Metabolic Rate
It is metabolic rate during the severest possible muscular exercise/athletes.
• Dietary Reference Intake (DRI)
The DRI consists of four dietary reference standards for the intake of
nutrients designated for specific age group, sex & physiologic states.
1. Estimated average requirement (EAR)
2. Recommended dietary allowance (RDA)
3. Adequate intake (AI)
4. Tolerable upper intake level (UL)
• Body Mass Index (BMI)
BMI (kg/m2) is the ratio of (wt in kg) ÷ (height in meters)2

11. Energy calculations
1. A person utilized 60 L O2 in one hour while he was walking. His RQ was 0.85. find out his energy
expenditure in 24hours while he was walking (at RQ 0.85, 1liter of O2 liberates 4.862 kcals).
2. In a test for BMR, a woman aged 40 yrs, 64 inch tall and weighing 125 pounds consumes 1200 ml
O2 at STP in 6 mins. Find out her BMR. (RQ 0.82, O2 Liberated 4.825 kcals).
3. An adult man of 70 kg body wt & surface area 1.7 sq. meter, basal requirements 40 C/sq meter/hr.
calculate Cal/24hr.
4. A young medical student aged 21yrs. having wt. 52kg and BMR 39, daily takes carbohydrates
210g, proteins 55g and fats 65g. How many kcals. does he consume each day.
5. A university student aged 32yrs, height 170cm and wt 68kg, consumed an average of 1.2 L of O2
at normal temperature & pressure in 6 min period. Calculate his BMR & % BMR deviation. (1
Liter O2 consumed = 4.825 C, surface area = 1.8 sq. meter).
6. A person consumes 250ml O2 and 200ml CO2 in 1 min. Calculate gas volumes in 24 hrs. Also
find out RQ.
Important Viva Questions:
 Define BMR & name factors effecting BMR.
 Enumerate condition increasing / decreasing BMR.
 Explain RQ and factors influencing RQ.
 Explain specific dynamic action of food.