ENERGY METABOLISM

The study of how the body uses, stores and burns energy ENERGY METABOLISM The study of how the body uses, stores and burns energy Carbohydrates Fats Proteins

ENERGY INPUT = ENERGY OUTPUT ENERGY BALANCE ENERGY INPUT = ENERGY OUTPUT Calories 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

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 Good agreement between direct and indirect 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 Carbohydrate 4.1 4 Fats 9.4 9 Proteins * 5.6 4* 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 = 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 = 1.0 FATS = 0.7 Proteins = 0.8 Mixed 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

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 = 0.3 x BMR Moderate = 0.4 x BMR Heavy = 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) +300 Kcal Lactation + 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 = 0.3 x BMR Moderate = 0.4 x BMR Heavy = 0.5 x BMR

ENERGY REQUIREMENTS Total = 2450 Kcal/day 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?

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

Most commonly used to assess obesity- Body Mass Index (BMI) Most commonly used to assess obesity- BMI = Wt (Kg)/Ht (m2) Underweight < 20.0 Normal (healthy) 20.0 – 24.9 Overweight 25.0 -29.9 Obese ≥ 30 Morbidly Obese > 45.1

= 120/(1.734)2 = 40.0 STEP 1 Calculate his BMI: BMI = Body wt. in Kg Height in m2 = 120/(1.734)2 = 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 = 160 lbs (~73 kg) 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

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