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Energy needs

Energy needs. Energy needs. Energy is require for all basic physiological functions Breathing Digestion Excretion Muscle function mobility heart Brain - most energy demanding Active transport pumps (cellular level). Energy needs: Units of measure of energy. Calories :

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Energy needs

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  1. Energy needs

  2. Energy needs • Energy is require for all basic physiological functions • Breathing • Digestion • Excretion • Muscle function • mobility • heart • Brain - most energy demanding • Active transport pumps (cellular level)

  3. Energy needs:Units of measure of energy • Calories: • Traditional unit • One calorie of heat raised the temperature of 1g of water through 1°C • Other Units • 1 kilocalorie = 1000 calories • Joules • SI unit • measure of energy exerted • 1 calorie = 4.18 joules • 1 kcal = 4.28 kJ

  4. Energy needs:How Much Energy do we need • We need to provide, from our food enough energy to; • Provide for body functioning • Maintain our temperature • Sustain physical activity • No more, no less • If take in too little energy, the body uses reserves it has put by and we lose weight • If we take in too much energy, the body stores the excess food, usually as fat and we put on weight

  5. Energy needs:Measurement of Energy Intake • Food possesses energy • Energy is released when food is converted, ultimately into Carbon dioxide and water • Energy content depends on food consumed • Total energy available is a function of Quantity of food consumed

  6. Energy needs:Measurement of Energy Intake • Different foods provide different amounts of energy for a given weight • Determined by composition of food • The following contribute to the energy content: • Carbohydrate • Fat • Protein • Alcohol

  7. Energy needs:Measurement of Energy Intake • The following do not contribute to the energy content: • Vitamins • Mineral • Water • Various methods have been developed to determine the energy content of food

  8. 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 • Heat of combustion represents the gross energy of the food • Energy lost during digestion and absorption • Affected by illness

  9. Energy needs:Measurement of Energy Intake Bomb Calorimeter

  10. Energy needs:Measurement of Energy Intake • Proximate Principles • The amount of energy which the body receives from food is known as metabolised energy • Calculated from Proximate principles • These are standardised energy contents of food based on typical composition • Found from on food composition tables

  11. Energy needs:Measurement of Energy Intake Metabolic Energy yields

  12. Energy needs:Measurement of Energy Intake • 100g of Potato crisps contain: • 49.3 g of Carbohydrates • 37.6g of Fat • 5.6g of Protein • 49.3 x 16 = 788.8 kJ from Carbohydrate • 37.6 x 37 = 1391.2 kJ from fat • 5.6 x 17 =95.2 kJ from protein • Total 2275.2 kJ

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

  14. Energy needs:Measurement of Energy Intake • Diet Surveys • Dietary and nutritional survey of British Adults (Gregory 1990) • Average UK dietary energy intake • Men 10.2 MJ • Women 7.02MJ

  15. Energy needs:Measurement of Energy Intake Sources of energy in the British diet (adults)

  16. Energy needs:Measurement of Energy Output Energy Output Energy of food ATP + Heat Loss • 50% efficiency ATP “Work” + Heat Loss • 50% efficiency “Work” Heat

  17. Energy needs:Components of Energy Output • Basal metabolic rate • Largest daily energy output • Definition: “the sum total of minimal activity of all tissue cells of the body under steady state conditions” • Osmotic pumps • Protein synthesis • Heart • Respiratory system • Digestive tract • Thermogenesis (Temperature maintenance) • Physical activity • Growth

  18. Energy needs:Basal Metabolic Rate • Body weight • Larger the body greater BMR • Lean body mass • Fat mass • Age • BMR highest in young infants • Falls with increase in age • 2% per decade after age of 30 • Decline in activity and proportion of lean tissue

  19. Disease Thyroid Fever Trauma Stress Drugs increase decrease Undernutrition Gender Women 10% higher body fat than men BMR lower for women Pregnancy Lactation Other Factors Genetics Climate Ethnicity Energy needs:Basal Metabolic Rate

  20. Energy needs:Basal Metabolic Rate W = body weight (kg)

  21. BMR example • A woman 40 years old, weight 62kg • = (0.034 x 62) + 3.538 • =2.108 + 3.538 = 5.646 • =5.7 MJ/day

  22. Energy needs:Components of Energy Output • Physical Activity • Most control • Differing levels of activity • Energy expended relates to body size • Physical activity ratios (PARs) • Physical activity level (PALs)

  23. Energy needs:Components of Energy Output

  24. Energy needs:Physical Activity Ratios

  25. Energy needs:Physical Activity Ratios • Bill is aged 40 and weighs 70kg • His BMR is calculate as follows: • (0.048 x 70) + 3.653 = 7.01MJ per day • Therefore:- • His hourly BMR =7.01/24 292kJ/hour

  26. Energy needs:Physical Activity Ratios • He records his daily activity pattern • Sleeping 7hours • Driving 2hours • Personal activities 3 hours • Watching TV 3hours • Playing football 1 hour • At work sitting at desk 8 hours

  27. Energy needs:Physical Activity Ratios - Example BMR/hr = 292 kJ/hr Total Energy use = 33.6 x 292 = 9811 kJ

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