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Metabolism and diet
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Metabolism and diet

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  • 1. Role of Metabolism in Nutrition
  • 2. Metabolism • Metabolism – people aquire and use free energy to carry out actions • Catabolism (degradation) – Nutrients and cell constituents are broken down for salvage and/or generation of energy • Anabolism (biosynthesis) - The process of releasing the energy that is consumed.
  • 3. Role of Metabolism in Nutrition Definition: the sum of all biochemical changes that take place in a living organism. Group these reactions into two types: anabolic catabolic Reactions: require energy release energy Produce: more complex compounds more simple compounds Modus Operandi: Occurs in small steps, each of which is controlled by specific enzymes.
  • 4. Examples of each type of metabolism: Anabolic Pathways Protein Biosynthesis Glycogenesis Gluconeogenesis Fatty Acid Synthesis Catabolic Pathways ATP Generated FOR Provides Energy Glycolysis TCA (Krebs cycle) ß-oxidation Respiratory Chain What you need to know is that Catabolic Pathways take sugars and carbs to turn them into ATP which is our major energy system. The anabolic pathways then allow your body to use the energy released by Catabolic pathways.
  • 5. Metabolism: Who Needs It? verage American consumes ~ 1450 lbs each year. (± 600kg) of f ssuming that 98.2% of this energy is etabolizable, 1424 lbs (± 590kg) is used to supply eeds. upplies roughly 1 x 106 kcals/ year
  • 6. How do we employ energy? • MECHANICAL- muscle contraction • ELECTRICAL- Use of internal organs. • CHEMICAL- transformation through catabolic and anabolic processes.
  • 7. 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: CHO: Fat: 17 kJ or 4 kcal/g 17 kJ or 4 kcal/g 37 kJ or 9 kcal/g
  • 8. Energy needs Measurement of Energy Intake Metabolic Energy Yields Fuel KJ/g Kcal/g Fat 38 9 Alcohol 29 7 Carbohydrates 17 4 Protein 4 16
  • 9. Energy needs Measurement of Energy Intake % Energy from carbohydrates, protein and fat Food Total energy % Energy content of from serving (kJ) carbohydrate % Energy from protein % Energy from fat Chocolate 1195 43 6 51 Peas 230 47 35 18 Chicken Breast 1138 0 75 24 Potato boiled 535 89 10 1
  • 10. Energy Balance: Input vs Output
  • 11. Energy Balance • Energy In = Energy Out – Weight Maintenance • Energy In > Energy Out – Weight Gain • Energy In < Energy Out – Weight Loss
  • 12. 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”
  • 13. Energy In • Food and Beverages – Food composition tables – Bomb Calorimetry • Complex social, environmental, physiological control
  • 14. Energy Out • Energy of food = Body Energy = ATP – Overall efficiency 25%, 75% released heat • Energy out: • 3 main components: – Basal Metabolic Rate – Thermic Effect Food – Physical activity
  • 15. BMR > Activity > Dietary Thermogenesis
  • 16. Energy needs Measurement of Energy Output Energy Output Energy of food • 50% efficiency ATP + Heat Loss ATP • 50% efficiency “Work “+ Heat Loss “Work “ Heat
  • 17. 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
  • 18. Factors affecting BMR • 1) Body Size & Composition ↑Lean tissue ↑BMR – Body weight ↑wt ↑lean tissue (but also ↑fat) • 2) Age: ↑age ↓Lean tissue • 3) Sex: Men ↑lean • 4) Activity: Exercise ↑lean tissue
  • 19. Factors affecting BMR • 5) Growth ↑BMR – Children, pregnancy • 6) Fasting/starvation: ↓BMR • 7) Fever/stress ↑BMR • 8) Smoking/caffeine: ↑BMR

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