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Nutrition and Metabolism

Nutrition and Metabolism. Objectives. Definition of metabolism, anabolism and catabolism. Ways of measurement of energy. Energy needs. Energy balance. Basal metabolic rate (BMR). Metabolism.

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Nutrition and Metabolism

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  1. Nutrition and Metabolism

  2. Objectives • Definition of metabolism, anabolism and catabolism. • Ways of measurement of energy. • Energy needs. • Energy balance. • Basal metabolic rate (BMR).

  3. Metabolism • Metabolism – process by which living systems acquire and use free energy to carry out vital processes • Catabolism (degradation) • Breakdown of nutrients and cell constituents and generation of energy (Exergonic oxidation) • Anabolism (biosynthesis) • Endergonic synthesis of biological molecules from simpler precursors • Coupled to exergonic processes through “high-energy” compounds

  4. Examples of each type of metabolism: Anabolic Pathways Catabolic Pathways Protein Biosynthesis Glycolysis Glycogenesis TCA (Krebs cycle) Gluconeogenesis ß-oxidation Fatty Acid Synthesis Respiratory Chain ATP Generated Provides Energy FOR

  5. How do we employ energy? • MECHANICAL-muscle contraction • ELECTRICAL-maintaining ionic gradients • (e.g., Na-K ATPase; 70% of • ATP used by kidney & brain • used to maintain gradient) • CHEMICAL- biotransformation of • molecules (e.g., synthesis • degradation, metabolism)

  6. International Unit of Energy: Joule : energy used when 1 Kg is moved 1 meter by a force of 1 Newton : kJ = 103 J; MJ = 106 J : 1 kcal = 4.184 kJ : Protein: 17 kJ or 4 kcal/g CHO: 17 kJ or 4 kcal/g Fat: 37 kJ or 9 kcal/g

  7. Energy needs Measurement of Energy Intake Metabolic Energy Yields

  8. Average Energy Needs: European text: 100 kJ/ day x BW in kg or 24 kcal/day x BW in kg American Biochem text: 129-184 kJ/ kg or 31-44 kcal/kg

  9. How to measure energy in food • Direct Calorimetry • Direct measurement of heat produced • Bomb calorimeter • Calculate • Calories/g: 4 (CHO), 9 (Fat) ,4 (Pro) and 7 (Alch) • based: lab analysis of food composition • Calorie chart or nutrient database

  10. Energy needs Measurement of Energy Intake Bomb Calorimeter • Food is ignited electrically in the presence of oxygen • Heat of combustion is measured from a rise in water temperature

  11. Bomb Calorimeter measures heat produced when food is burned

  12. Text view of bomb calorimeter

  13. Energy needs Measurement of Energy Intake Bomb Calorimeter • Heat of combustion represents the gross energy of the food • Energy lost during digestion and absorption • Affected by illness

  14. Energy needs Measurement of Energy Intake % Energy from carbohydrates, protein and fat

  15. Energy Balance: Input vs Output

  16. Energy Balance • Energy In = Energy Out • Weight Maintenance • Energy In > Energy Out • Weight Gain • Energy In < Energy Out • Weight Loss

  17. Energy Balance • Sources of fuel for energy • Input from diet: carbs, fat, prot, alcohol • Stored energy: glycogen, fat, muscle • Energy outgo from: • Basal metabolism • Physical activity • “Dietary thermogenesis”

  18. Energy In • Food • Food composition tables • Bomb Calorimetry • Complex social, environmental, physiological control

  19. Energy Out • Energy of food = Body Energy = ATP • Energy out: • 3 main components: • Basal Metabolic Rate • Thermic Effect Food • Physical activity

  20. BMR > Activity > Dietary Thermogenesis

  21. Energy needs Measurement of Energy Output Energy Output • Two methods • direct calorimetry • indirect calorimetry Measurement of heat Measurement of energy used

  22. Energy needs Measurement of Energy Output direct calorimetry • Measurement of heat loss

  23. Energy needs Measurement of Energy Output Indirect calorimetry • Utilization of oxygen • Oxygen consumption is proportional to ATP synthesis • Use oxygen consumption to determine heat production

  24. Energy needs Measurement of Energy Output Indirect calorimetry • Glucose oxidation • Starch oxidation 6H2O + 6CO 2 C6H12O6 + 6O2 + 15.5 kJ/g of energy 5nH2O + 6nCO 2 (C6H12O5)n + 6nO2 + 17 kJ/g of energy

  25. Energy needs Measurement of Energy Output Indirect calorimetry • Fat oxidation (e.g. glyceryl butro-oleostearate (main fat in butter) C3H5O3.C4H7O.C18H33O. C18H35O + 60O2 + + 43CO2 40H2O 39 kJ/g of energy

  26. Energy Out: Basal Metabolism • Largest daily energy output • Definition: “the sum total of minimal activity of all tissue cells of the body under steady sate conditions” • Men estimate: lbs body weight X 11 • Women estimate: lbs body weight X 10 • affected by • Muscle > Fat Male > Female • Young > Old • Temperature: body and environment

  27. Basal Metabolic Rate • BMR = number of calories would need daily simply to stay alive if were totally inactive, in bed, awake for 16 hours & slept for 8 hours • Harris-Benedict Equation: • Women: 661+(4.38 x weight in pounds)+(4.38 x height in inches)-(4.7 x age)=BMR • Men: 67+(6.24 x weight in pounds)+(12.7 x height in inches)- (6.9 x age)=BMR

  28. James & Schofield

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