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Energy Metabolism and BMR

Energy Metabolism and BMR. Energy: Metabolism. ‘Metabolism refers to chemical process that occur in the body that are necessary to maintain life.’ (Magee & Oliver 2010) Metabolism involves two key processes: Catabolism

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Energy Metabolism and BMR

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  1. Energy Metabolism and BMR

  2. Energy: Metabolism • ‘Metabolism refers to chemical process that occur in the body that are necessary to maintain life.’ (Magee & Oliver 2010) • Metabolism involves two key processes: • Catabolism • Substances are broken down into simpler substances. For example, carbohydrate is converted to glucose. • Anabolism • Larger molecules or structures are built from smaller ones. For example, proteins build body tissue. • Energy is released during catabolic reactions to create (adenosine triphosphate)

  3. Carbohydrate Metabolism

  4. Lipid Metabolism

  5. Protein Metabolism

  6. Energy: Storage and Balance Storage of metabolised food is essential for times of famine and when the body requires great energy output. Storage occurs in cells in the form of either glycogen or triglycerides. If the body’s energy needs are in balance, energy consumption equals energy expenditure.

  7. Energy: Storage and Balance • The body requires energy for: • Maintaining body temperature (heat energy) • Brain and nerve transmission (electrical) • Movement (mechanical) • Digestion and Metabolism (chemical energy) • The energy is easily transferred from one form to another depending on the body’s requirements.

  8. Basal Metabolic Rate (BMR) Only 30% of energy intake is used for physical activity. Remaining 70% is used for all the other metabolic processes that occur in the body. Basal energy is the minimum amount of energy used to maintain normal body temperature and muscle tone, to keep the heart beating and all vital organs functioning. The rate at which energy is needed for these metabolic processes is called the Basal Metabolic Rate.

  9. How to calculate BMR? • Turn to p52 and complete activity 11.

  10. Influences on BMR • Body size • The larger the body the greater the BMR due to increased energy demands • Body fat • Fatty tissues have a lower BMR than muscle tissue. Therefore, greater lean body tissue increases your metabolic rate, because it is an active tissue that burn kilojoules at a faster rate.

  11. Influences on BMR • Hormones • People with an overactive thyroid have a higher BMR. • Illness • Increased BMR as the body works harder to fight infection • Fasting • Reduces BMR, because the body conserves energy to keep vital organs functioning.

  12. Influences on BMR • Drugs • Caffeine and nicotine increase BMR • Anti-Depressants, social and prescription drugs reduce BMR • Exercise • BMR increases during exercise. BMR remains high during intense prolonged activity. • Gender • Males have an elevated BMR than females

  13. Influences on BMR • Climate • Cold temperatures increase BMR given the body uses energy to stabilise body temperature. • Age • Decreases with age due to less activity and reduce lean tissue

  14. Energy Balance • To identify a person’s energy balance you must calculate energy intake and expenditure. • If intake is higher than expenditure a person will store energy. • If intake is lower than expenditure a person will burn energy. • To calculate daily energy intake list all the food and beverages consumed. Using a food kilojoule table work out their values. • Energy Expenditure for the day = BMR + thermic effect + exercise • Calculate BMR • Take into account the thermic effects of food (10%) • Work out the kilojoule expenditure for various activities.

  15. Thermic Effect of Food ‘…the energy used in digestion, absorption, metabolism and the storage of ingested nutrients.’ Thermic effect is estimated at 10% of energy intake.

  16. Energy Expenditure Calculation Example (p53) 73kg female consuming 8500 kJ walked for 30 minutes using 462 kJ and cycled for 60 minutes using 1344 kJ BMR = 73 X 0.9 X 24 = 1576.8 calories = 1576.8 x 4.2 = 6623kj Thermic effect = .10 X 8500kj = 850kj Energy Expenditure for the day = 6623 + 850 + 1806 = 9279kj Energy balance = Intake – Expenditure 8500kj – 9279kj= 779kj

  17. Your Turn – Calculate Energy Balance 68kg male consuming 11000kjwho jogged for 30 minutes (300 calories) and cycled for 1.5 hours (420 calories) BMR = 68 x 1.0 x 24 = 1632calories = 1632 x 4.2 = 6854kj Thermic Effect = .10 x 11000kj = 1100kj Energy Expenditure = 6854 + 1100 + 1260 +1764= 10978kj Energy Balance = 11 000 – 10978 = 22kj

  18. Your Turn – Calculate Energy Balance Female 62kg consuming 6985 kJ and burning 486 calories in daily activities. BMR = 62kg x 0.9 x 24 = 1339.2 = 1339.2 x 4.2 = 5625 kj Thermic Effect = 6985 x .10 = 699kj Energy Expenditure = 5625 + 699 + 2041 = 8365kj Energy Balance = 6985 – 8365 = - 1380kj

  19. Body Mass Index (BMI) BMI is a measure of weight for height. BMI does not distinguish between weight due to fat or weight due to muscle. BMI data developed based on data from Anglo-Saxon background; thus, height, weight and fat distribution among different ethnic groups is not taken into account.

  20. BMI

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