Unit5: Nutrition: Energy
- What is the standard unit of energy in foods?
- How are calories and joules related?
1Kilocalorie (Kcal or C) = 4.184 K Joule
- What are the four main factors that affect the energy value of foods?
- Composition of food
- Water or the moisture content of food
- Fat content in the food
- Food preparation or processing methods
- What are the four different categories for which energy is required by the body?
- Energy for basal metabolism (Involuntary)
- Energy for muscular activity (Voluntary)
- Energy for utilization of food
- Energy for growth and repair of tissues
- What are the factors that affect the energy requirement of the body?
- Age
- Sex
- Body size
- Climate
- Secretion of endocrine glands
- Status of health
- Altered physiological states
- Effect of food
- Extent of physical activity
- How to calculate the energy requirement of an individual?
Method
- Calculate the energy required for the basal metabolism. For men, 26 kcal/kg body weight. For women, 24 kcal/kg body weight.
- Calculate the energy required for physical activity
- Add both the requirements.
- Add 10% for the thermogenesis effect of food.
Energy required for BMR = 26 kcal/kg body weight = 70 x 26 = 1820 kcal
Energy required for physical activity = (Add 30-40% of BMR)
= (40/100 x 1820) + 1820
= 728 + 1820 = 2548 kcal
Additional 10% energy required for thermogenesis
= 2548 x 10% = 254.8 kcal
Total energy Requirement = 2548 + 254.8 = 2802.8 kcal/day
The Total Energy Requirement for an adult man of 70 kg doing sedentary work = 2800 kcal/day
This gives the total energy required by the individual
- What are the two different methods used to measure the energy released by an individual and the amount of energy released by the foods?
- Direct calorimetry
- Indirect calorimetry
- How is the body mass index calculated?
Body Mass Index (BMI)= (Weight in Kilograms) / (Height in metres)2 = wt (kg) / Ht2 (m)
= 58kg/(162cm)2 = 58kg / (1.62 m)2 = 58/2.62 = 22.1
If BMI ≥ 25, ==> overweight
If BMI ≥ 30, ==> obese
Normal BMI value for Men à 20 – 25
Normal BMI value for Women à 19 – 24
Table showing Classification of adults according to BMI
- Define BMR
Or in simple words
The amount of energy required by a person who is awake, but he is nearly at complete mental and physical rest and had no food for 12-14 hours is known as basal metabolism. Basal metabolic rate refers to minimum amount of energy required by the person to survive.
The amount of energy required to carry on the involuntary work of the body is known as basal metabolic rate. It includes the functional activities of various organs such as brain, heart, liver, kidney, lungs, and the peristaltic movement of gastrointestinal tract, maintenance of muscle tone and body temperature. The brain and nervous tissue accounts for about 1/5th of the energy utilized and the rest by the other parts of the body.
Involuntary actions are activities such as expansion and contraction of the heart, respiration and digestion. Involuntary actions include energy needed for body maintenance and is known as the basal metabolic rate.
This energy must be supplied to the body first, because energy required by the heart for its normal functioning or for the constant supply of blood to the brain are vital functions upon which survival of a being depends.
- What are the conditions that should be taken care of before measurement of BMR?
- The person should be in a Post-absorptive State. The patient should not have taken anything by mouth for the past 12 hours.
- Complete mental and physical relaxation.
- Patient should be awake.
- Recumbent position during the test.
- Environmental temperature should be between 20°C-25°C
- How is BMR calculated?
- Calculation of BMR using Benedict and Roth apparatus
It has already been mentioned that for finding out the metabolic rate, two values, i.e., the amount of O2 consumed by the subject during a known period of time and his Respiratory Quotient (R.Q.) during this interval, are to be determined. However, the determination of Respiratory quotient (R.Q.) is not necessary for calculating Basal Metabolic Rate (BMR). This is because, in a large number of experiments, it was found that the RQ of a person under basal conditions in the post-absorptive state remains constant at 0.82. At this RQ, 1 litre of O2 liberates 4.825 Cals.
Subject: Adult male, 50 kg body weight
Oxygen consumed in 6 minutes: 1100 ml =1.1 L
We know from the above explanation that 1L of O2 liberates 4.8 calories of energy
So, 1.1 L of oxygen would liberate 4.8 x 1.1Cal/Kcal of energy.
So, the heat produced in 6 min is = 5.28Cal/Kcal
The heat produced in 24 hours is = 5.28 x60 x24 = 1276.2
6
- Calculation of surface area using Du Bois formula
We get the calories measurement through Benedicts Roth experiment. To get the measurement of the surface area we use Du Bois formula
A = H0.725 x W0.425 x 71.84,
Where A = surface area in cm2
H = height in cm
W = weight in kg
The above value obtained is in sq. cm. This should be divided by 10,000 to get the surface area in sq. metre.
- Are there any other methods also that can help in the calculation of BMR?
1
By Body Weight
For Female – Weight (kg) x 0.9 kcal x 24 hrs
For Male – Weight (kg) x 1 kcal x 24 hrs
2
By Harris – Benedict Equator
For Female – 65.5 + ( 9.56 x W (kg)) + (1.85 x H (cm)) – (4.68 x A)
For Male – 66.5 + (13.75 x W (kg)) + (5.0 x H (cm)) – (6.75 x A)
3
By using Metabolic body size – 70 x Wt in kg(3/4)
4
By FAO / WHO / UNU equation
For Female – 8.7 x W + 829
For Male – 11.6 x W + 879
In the case of formula given by FAO/WHO, this BMR calculation is for the age group 30-60 yrs.
- What are the factors that affect BMR
a. Surface Area: The BMR is directly related to the surface area of the subject. Larger the surface area, greater would be the BMR.
b. Age: The BMR is inversely proportional to age. Children have larger BMR than adults.
c. Sex: Males have higher BMR than females. The BMR of females declines more rapidly between the ages of 5 and 17 than that of males.
d. Climate: The BMR is lower in warm climates.
e. Racial Variations: The BMR of oriental women living in the USA is 10 per cent below the standard BMR of American women of the same age.
f. Habit: Persons accustomed to heavy exercise or hard physical work have a higher BMR than those involved in sedentary work.
g. State of Nutrition: The BMR is decreased in starvation and undernourishment.
h. Pregnancy: The BMR is not changed during pregnancy. The higher values of BMR in late pregnancy is due to the BMR of the foetus.
i. Disease: The BMR is increased in infectious and febrile diseases. The increase is usually proportional to the rise of the temperature. The BMR is also increased in increased activity of cells and, therefore, it increases in leukaemia, cardiac failure, hypertension, polycythaemia, dyspnoea, and some types of anaemia.
j. Effects of Hormones: The BMR is increased in hyperthyroidism and decreased in hypothyroidism. In adrenal insufficiency (Addison’s disease), the BMR is subnormal.
k. Drugs: Caffeine and benzidine increase the BMR.
l. Emotion: The BMR is increased in emotional stress.
m. Diet: The BMR of strict vegetarians is 11% lower than that of meat eaters.