ENERGY METABOLISM

ENERGY METABOLISM

The study of how the body uses, stores and burns energy

CarbohydratesFats Proteins

ENERGY BALANCE

ENERGY INPUT = ENERGY OUTPUTCalories from food intake

= Digestion,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

• Equilibrium input = output, no weight change

• Positive energy balanceinput > output, increase in weight(necessary during pregnancy, for infants and children)

• Negative energy balanceinput < output, decrease in weight

ENERGY BALANCE

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 FOODSCALORIMETERkcal/g

BODY kcal/gMETABOLIZABLE ENERGY

Atwater Factors

Carbohydrate 4.1 4Fats 9.4 9Proteins * 5.6 4*Alcohol 7.0 7Fiber No calories -* The difference is due to energy content of urea, which cannot be further metabolized in the body

QuestionMr. I.L. Nihari consumes 585 g carbohydrates, 150 g protein110 g fatHow many calories a day is he consuming?

585 x 4 = 2,340 kcal150 x 4 = 600 kcal110 x 9 = 990 kcalTOTAL = 3930 kcal/day

CO2 O2

INDIRECT CALORIMETRY

INDIRECT CALORIMETRY

Vol of CO2 produced

Vol of O2 consumed

C6H12O6 + 6O2 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 =

RESPIRATORY QUOTIENT

CARBOHYDRATE = 1.0FATS = 0.7Proteins = 0.8Mixed diet = 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

• 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/dayFemales 1200 – 1450 kcal/day

BASAL METABOLIC RATE (BMR)/ RESTING METABOLIC RATE (RMR)

FACTORS AFFECTING BMRIncrease• 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 lactationDecrease• 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 = 0.3 x BMRModerate = 0.4 x BMRHeavy = 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 FACTORS AFFECTING ENERGY REQUIREMENTS 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 FACTORS AFFECTING ENERGY REQUIREMENTS REQUIREMENTS

PHYSICAL ACTIVITY:The most important factorFor person with very heavy physical activity add

600-900 Kcal

PREGNANCY AND LACTATION:

Pregnancy (2nd and 3rd Trimester) +300 KcalLactation + 500

Kcal

ENERGY REQUIREMENTS

* MOST COMMONLY USED METHOD (TEF is ignored)

Energy REQ = BMR + Physical Activity

1. BMR = wt (kg) x 25 Kcal2. Physical Activity:

Modest = 0.3 x BMRModerate = 0.4 x BMRHeavy = 0.5 x BMR

ENERGY REQUIREMENTS

Example: 70 Kg Man, Moderately Active

BMR = 70 x 25 = 1750 Kcal

Physical activity = 0.4 x 1750 = 700 Kcal

Total = 2450 Kcal/day

How to lose excess body wt?

Mr I. L. NihariHe 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?

CASE

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 < 20.0Normal (healthy) 20.0 – 24.9Overweight 25.0 -29.9Obese ≥ 30Morbidly Obese > 45.1

STEP 1

Calculate his BMI:

BMI = Body wt. in KgHeight in m2

= 120/(1.734)2 = 40.0

STEP 2

Calculate his caloric requirement on the basis of current body weightCaloric 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 4Calculate his adjusted body weight

adjusted body weight = Ideal body weight + 25% of (current body weight - ideal body weight)

73 + 11.8 = 84.8 kg

Calculate his caloric requirement on the basis of adjusted body weightCaloric requirement = BMR + Physical activity (modest)

(BMR x 0.3)

84.8 x 25 = 2120 + 636 = 2756 kcal/day

STEP 5

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 6

Caloric Intake needed/day = 2756 – 513 = 2243 ≈2250 Kcal/day

(2756 = Adjusted body wt. basis)

STEP 7

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

• EXERCISE : Exercise (walk 1-2 miles/day or other physical activities)

• BEHAVIOUR MODIFICATION

ADVICE FOR CHANGE IN LIFE STYLE

THE ENDTHE END