1. Energy needs

2.  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: 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.  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 Energy needs: Energy needs: Measurement of Energy Intake

6.  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 Energy needs: Energy needs: Measurement of Energy Intake

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

8.  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 Energy needs: Energy needs: Measurement of Energy Intake

9. Bomb Calorimeter

10.  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 Energy needs: Energy needs: Measurement of Energy Intake

11. Metabolic Energy yields

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

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

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

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

17.  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 Energy needs: Energy needs: Components of Energy Output

18.  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 Energy needs: Energy needs: Basal Metabolic Rate

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

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

24. Energy needs: Energy needs: Physical Activity Ratios ActivityPAR Sleep1.0 Quiet sitting 1.2 Active sitting 1.6 Stationary standing 1.6 General Mixed (personal activities) 1.4 Activities requiring moving about 2.1 Walking2.8 Gardening3.7 Swimming4.8 Running6.0

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