Metabolism and Energy Balance PDF

Metabolism and Energy Balance Dr. Alper YILDIRIM [email protected]  Objectives What is metabolism? Energy balance? Regulation of feeding What is metabolic rate and how do we measure it? – Factors that effecting metaboli...

Metabolism and Energy Balance Dr. Alper YILDIRIM [email protected]  Objectives What is metabolism? Energy balance? Regulation of feeding What is metabolic rate and how do we measure it? – Factors that effecting metabolic rate  Metabolism Chemical Reactions LIFE ! Proteins Fats Breaking down Carbohydrates Nucleic acids Catabolism Obtain ATP Building up Food Anabolism ADP Digestion Catabolism fuels Anabolism - Amino acids - Fatty acids - Glucose - Nucleotides Anabolism Catabolism Hormones regulates this process Metabolism describes every single biochemical reaction in your body Nutrient pools and Metabolism Fates of Nutrients in Fed-State and Fasted-State Metabolism Energy Balance Appetite and Satiety Hypothalamus Feeding Center Satiety Center  Appetite and Satiety Key Peptides that Modulate Food Intake Appetite and Satiety Energy Balance  Energy Balance Oxidation of 1 g of (Redox)  Protein 4.3 kcal  Carbohydrate 4.1 kcal  Fat 9.3 kcal Water, minerals, vitamins and cholesterol = No energy Fuel Content of a 70kg Person  Energy Balance Oxygen Consumption Reflects Energy Use Direct calorimetry Indirect calorimetry For food Measuring the amount of oxygen consumed by the body The body liberates app. 4.825 kcal during the utilization of 1 L of O2 Example: O2 consumed = 15.2 L/h 15.2 x 4.8 = 73 kcal/h (energy liberated=metabolic rate)  Metabolic Rate Metabolic rate is calculated by multiplying oxygen consumption by the number of kilocalories metabolized per liter of oxygen consumed: A mixed diet with an RQ of 0.8 requires 1 liter of O2 for each 4.80 kcal metabolized. For a 70- kg male whose resting oxygen consumption is 430 L/day, this means: Respiratory Quotient (RQ) RQ = CO2 produced / O2 consumed For carbohydrates: RQ= 1 Example: For fats: RQ= 0.7 Oxidation of glucose For proteins: RQ= 0.8 C6H12O6 + 6O2 6 CO2 + 6 H20 + heat CO2 / O2 = 6 /6 = 1= RQ  Factors affecting the metabolic rate Exercise Muscle contraction liberates large amounts of heat compared to resting state. Daily energy requirement just for existing is appr. 2000 kcal  Factors affecting the metabolic rate Specific dynamic action of proteins After a meal containing large quantities of proteins, the metabolic rate rises within 1h and lasts for 3-12h. Age Metabolic rate decreases from birth until old ages. Thyroid hormones Increase the metabolic rate Sympathetic stimulation NP and EP have a direct effect on muscle and liver cells to induce glycogenolysis and to increase cellular activity.  Factors affecting the metabolic rate Gonadal hormones Testosterone increases the metabolic rate by 10-15% Growth hormone Increases metabolic rate as a result of direct stimulation of cellular metabolism Fever Increases the rate of all chemical reactions Climate Metabolic rate of people living in hot climate is lower than of people living in cold regions Sleep Metabolic rate decreases 10-15% below Malnutrition Prolonged fasting decreases the metabolic rate You are responsible from Guyton & Hall Textbook of Medical Physiology 13th Edition Chapter 72 and 73