Download ENERGY METABOLISM

ENERGY
METABOLISM
ENERGY METABOLISM
The study of how the body uses, stores and burns
energy
Carbohydrates
Fats
Proteins
ENERGY BALANCE
ENERGY INPUT = ENERGY OUTPUT
Calories from
= Digestion,
food intake
metabolism, transport
of nutrients, physical
activity
Maintenance of energy balance
- contributes to health and well being
- prevents the risk of developing many common
health problems
ENERGY BALANCE
• Equilibrium
input = output, no weight change
• Positive energy balance
input > output, increase in weight
(necessary during pregnancy, for infants and
children)
• Negative energy balance
input < output, decrease in weight
Energy balance – Some
questions??
• How much energy is contained a particular
meal? Different foods?
• How can the energy in foods be measured?
• How can energy expended by an individual be
measured?
i.e., how would you measure energy input and
out put???
CALORIMETRY
production
Good agreement between direct and indirect calorimetry
ENERGY VALUES OF FOODS
1 Kilocalorie = amount of heat required to raise
the temperature of 1 kg of water through 1˚C
(15˚ to 16˚C).
1 kcal = 1 Calorie (capital C) in nutrition
1 kcal = 4.184 kilojoules
BOMB CALORIMETRY
DIRECT CALORIMETRY
ENERGY VALUES OF FOODS
CALORIMETER
kcal/g
BODY kcal/g
METABOLIZABLE
ENERGY
Atwater Factors
Carbohydrate
4.1
4
Fats
9.4
9
Proteins *
5.6
4*
Alcohol
7.0
7
Fiber
No calories
* The difference is due to energy content of urea, which cannot be
further metabolized in the body
Question
Mr. I.L. Nihari consumes
585 g carbohydrates,
150 g protein
110 g fat
How many calories a day is he consuming?
585 x 4 = 2,340 kcal
150 x 4 = 600 kcal
110 x 9 = 990 kcal
TOTAL = 3930 kcal/day
CO2
O2
INDIRECT CALORIMETRY
INDIRECT CALORIMETRY
Respiratory
Quotient
=
C6H12O6 + 6O2
Vol of CO2 produced
Vol of O2 consumed
6CO2 +6H2O + Heat 664 Kcal
Therefore R.Q. for glucose oxidation = 6/6 = 1
C15H31COOH + 23O2
16CO2 + 16H2O + 2313Kcal
Therefore R.Q. for Palmitic acid oxidation = 16/23 = 0.7
RESPIRATORY QUOTIENT
CARBOHYDRATE
FATS
Proteins
Mixed diet
= 1.0
= 0.7
= 0.8
= 0.85
R.Q. > 1.0 Carbohydrates  Fats
R. Q. = 0.7 Starvation, Diabetes
DAILY ENERGY EXPENDITURE
DEE = Basal metabolic rate + physical activity +
Thermic effect of food + Thermogenesis
BASAL METABOLIC RATE (BMR)/
RESTING METABOLIC RATE (RMR)
• BMR: The energy expenditure of a person
mentally and bodily at rest in a thermoneutral
environment 12-18 hours after a meal
• For a sedentary person BMR accounts for 60% to
70% of the total body energy expenditure
• Functioning of lungs, heart, kidneys, brain;
maintenance of ionic gradients; reactions of
metabolic reactions…..
• RMR: If a person is not fasting or completely rested
• Typically 6% higher than the BMR
BASAL METABOLIC RATE (BMR)/
RESTING METABOLIC RATE (RMR)
• BMR is calculated by measuring O2 consumption for 6
min and using the following factor
one liter of O2 consumed = 4.825 kcal
Q: If 1.5 liters of O2 are consumed in 6 minutes calculate
the BMR of a patient .
• Approx equal to 25 kcal/kg/day
Males 1600 -1800 kcal/day
Females 1200 – 1450 kcal/day
FACTORS AFFECTING BMR
Increase
• Lean body mass
• Larger surface area
• Sex (M > F)
• Body temperature: in fever 30-35%  at 40˚C
(104oF)
• Nervous sytem activity (release of norepinephrine)
• Hormones, esp. Thyroid hormone
• pregnancy and lactation
Decrease
• Low calories intake
• Aging
DAILY ENERGY EXPENDITURE
DEE = Basal metabolic rate + physical activity +
Thermic effect of food + Thermogenesis
PHYSICAL ACTIVITY
• Most important factor in determining the DEE
of an individual
Modest
Moderate =
Heavy
=
0.3 x BMR
0.4 x BMR
=
0.5 x BMR
DAILY ENERGY EXPENDITURE
DEE = Basal metabolic rate + physical activity +
Thermic effect of food + Thermogenesis
Thermic effect of food
•
•
•
Energy required to digest, process and absorb food
Also known as Specific Dynamic Action
 O2 consumption associated with digestion and
absorption of foods
•
Protein 12% of total energy expenditure
•
Carbohydrates 6% of total energy expenditure
•
Fats 2% of total energy expenditure
•
Mixed diets 5-10% of total energy expenditure
•
3000 Kcal diet, TEF 150-300 kcal
DAILY ENERGY EXPENDITURE
DEE = Basal metabolic rate + physical activity +
Thermic effect of food + Thermogenesis
FACTORS AFFECTING ENERGY
REQUIREMENTS
1. BODY SIZE:  with an  in muscle mass
2. AGE :
22 – 50 yrs
supposing at 2000 Kcal
51- 75 yrs 90% of age 22-50 yrs – 1800 Kcal
>75 yrs
75-80% of age 22-50 yrs – 1500/1600
Kcal
FACTORS AFFECTING ENERGY
REQUIREMENTS
PHYSICAL ACTIVITY:
The most important factor
For person with very heavy physical activity add
600-900 Kcal
PREGNANCY AND LACTATION:
Pregnancy (2nd and 3rd Trimester)
Lactation
+300 Kcal
+ 500 Kcal
ENERGY REQUIREMENTS
* MOST COMMONLY USED METHOD (TEF is ignored)
Energy REQ = BMR + Physical Activity
1. BMR = wt (kg) x 25 Kcal
2. Physical Activity:
Modest
=
Moderate
=
Heavy
=
0.3 x BMR
0.4 x BMR
0.5 x BMR
ENERGY REQUIREMENTS
Example: 70 Kg Man, Moderately Active
BMR =
70 x 25
Physical
activity
=
=
0.4 x 1750 =
1750 Kcal
700 Kcal
Total = 2450 Kcal/day
How to lose excess body wt?
CASE
Mr I. L. Nihari
He is 5’9’’ tall & weighs 264 lbs (120 kg).
The doctor has advised him to lose 10 kg over a period of 5
months.
Q. what should be his caloric intake to reduce the weight?
Q. How many calories would he need to decrease per day to
achieve the desired target?
Q. What weight reduction plan would you advise this
patient?
Diagnosis of Overweight and
Obesity
– Height-weight tables
– Light, medium & heavy frame
– Skin-fold thickness (specific areas)
Triceps
– Body Mass Index
Body Mass Index (BMI)
Most commonly used to assess obesity-
BMI = Wt (Kg)/Ht (m2)
Underweight
Normal (healthy)
Overweight
Obese
Morbidly Obese
< 20.0
20.0 – 24.9
25.0 -29.9
≥ 30
> 45.1
STEP 1
Calculate his BMI:
BMI = Body wt. in Kg
Height in m2
=
2
120/(1.734)
= 40.0
STEP 2
Calculate his caloric requirement on the
basis of current body weight
Caloric requirement =
BMR + Physical activity (modest)
(BMR x 0.3)
120 x 25 = 1875 + 900 = 3,900 kcal
STEP 3
Calculate his ideal body weight
Ideal body weight = 100 + (5 x 3)
(100 lbs for 5 ft; 5 lbs for every inch above
5 ft for women
106 lbs for 5 ft; 6 lbs for every inch above 5
ft for men)
= 160 lbs (~73 kg)
STEP 4
Calculate his adjusted body weight
adjusted body weight =
Ideal body weight + 25% of (current body
weight - ideal body weight)
73 + 11.8 = 84.8 kg
STEP 5
Calculate his caloric requirement on the
basis of adjusted body weight
Caloric requirement =
BMR + Physical activity (modest)
(BMR x 0.3)
84.8 x 25 = 2120 + 636 = 2756 kcal/day
STEP 6
How many grams of body weight does he need to
reduce per day?
(10 kg in 5 months)
10 kg in 5 months =
2 Kg / month = 2000/30 = 67g/day
Caloric value of 67g adipose tissue
(85% fat, 15% water) = ?
67 x 9 x 0.85 = 513 Kcal
STEP 7
Caloric Intake needed/day =
2756 – 513 = 2243
≈2250 Kcal/day
(2756 = Adjusted body wt. basis)
Comparison of energy
requirements at various body
weights
• Current body weight = 3900 - 513 =
3387 Kcal
• Ideal Body weight
= 2372 - 513 =
1859 Kcal
• Adjusted body weight = 2756 – 513 =
2250 Kcal
•
•
•
•
•
ADVICE FOR CHANGE IN LIFE
STYLE
DIET: Eat a balanced diet, low in Calories
FAD DIETS DON’T WORK
↓ intake of high caloric density foods
• Fried foods, sweets etc.
Substitute low fat milk for whole milk
Low fat yogurt for full fat yogurt
 the intake of vegetables & fruits (Foods
with high fiber content, Rich in vitamins &
minerals
ADVICE FOR CHANGE IN LIFE
STYLE
• EXERCISE :  Exercise (walk 1-2
miles/day or other physical activities)
• BEHAVIOUR MODIFICATION
THE END