Download - Energy Intake and Expenditure
Energy intake and expenditure
Mariam Abdul Latif & Dr Yasmin Ooi 20 July 2008
26 September 2013
School of Food Science and Nutrition
Learning outcomes After completing this module, students should be able to:
• explain, differentiate and measure energy intake, energy expenditure and energy requirements.
• understand the concept of energy balance and apply it in explaining body weight gain and biased reporting of energy intake (practical)
• Describe factors that influence energy expenditure
Next semester Nutrition throughout the lifecycle
• Energy balance in various conditions: – Infancy and childhood – Adulthood – Aging
• Energy requirements in: – Physically active groups – Pregnancy and lactation – Disease and trauma (in detail in Dietetics)
Introduction
• The average human consumes close to 1,000,000 calories (4,000 MJ) per year.
• Consider this: 500 MJ is approximately the explosive energy of 100 kg of TNT.
• We eat the same amount of energy from 800 kg of TNT in a year.
• Yet, for most people, we manage to achieve energy balance, neither losing weight or putting on weight.
Terminology
• Energy intake • Energy storage • Energy expenditure • Energy requirement • Energy balance • Metabolisable energy intake
Energy intake • Human consumes plants and animal products –
breaking down CHOs, fats & protein (during digestion) releasing energy & nutrients
• The body makes use of the energy from the macronutrients (CHO, fats, protein).
• Energy intake = caloric or energy content of food as provided by the major sources of dietary energy:
– carbohydrate (16.8 kJ/g), – protein (16.8 kJ/g), – fat (37.8 kJ/g) and – alcohol (29.4 kJ/g)
Calculating Food Energy • Bomb calorimeter • Weighed food sample
ignited with an electric spark –burned in an oxygenated atmosphere
• The container is immersed in a known volume of water
• The rise in the temperature of the water after igniting the food is used to calculate the heat energy generated
1000 calories = 1 kilocalorie = 1 kcal = 4.2 kJoule the energy it takes to raise the temperature of 1kg of water by 1°C.
Energy value of food
• Not all energy in foods &
alcohol is available to the
body cells
• Processes of digestion &
absorption are not
completely eficient
• Fiber : 2 kcal/g –
‘unavailable carbohydrate’
that resists digestion and
absorption (Guenther &
Jensen 2000)
Calculation • How much is the energy value of a 50
gm butter cake with icing calculated in terms of weight is derived from protein (15%), fat (11%) and carbohydrate (3%).
• Protein: 15% x 50 gm = 7.5 gm X 4 kcal/g = 30 kcal • Fat : 11% x 50 gm = 5.5 gm =5.5 gm X 9 kcal/g
= 49.5 kcal • Carbohydrate: 3% x 50 gm = 1.5 gm X 4 kcal/g
= 6 kcal • Total energy: 85.5 kcal = 359.1 kJ
Energy storage • Energy storage = the energy consumed can be: • Stored
– Fat (major energy store) – Glycogen (short-term energy or carbohydrate
reserves) – Protein (rarely used except in severe cases of
starvation or wasting conditions) • Used
– To fuel energy-requiring events
Components of Energy Expenditure
ENERGY EXPENDITURE
Basal metabolic rate (BMR)
~ 60-‐75%
Thermic effect of food (TEE) ~10%
Energy expended in physical acMvity (PAL)
~ 15-‐30%
Energy expenditure • The energy intake (consumed in the form
of food) is used by the body for metabolic, cellular and mechanical work (e.g. breathing, muscular work).
• Energy expenditure can be divided into: – Basal metabolic rate (BMR) / resting metabolic
rate – Thermogenesis / thermic effect of food (TEE) – Physical activity / thermic effect of exercise – Others
Other energy expenditure – Growing in individuals (negligible except
within the first few months of life) – Adaptive thermogenesis (e.g. exposure to
reduced temperatures, rarely occurs in human except during the first few months of life, fever, other pathological conditions)
– Other activities contributing to thermogenic effects – nicotine (smokers may have a 10% higher energy expenditure), caffeine, capsaicin (in hot chillies)
Back
Resting metabolic rate (RMR) • RMR : the energy expended in the activities necessary
to sustain normal body functions & homeostasis • Incl. respiration & circulation, synthesis of organic
compounds, pumping of ion across membranes, energy required by central nervous system, maintain body temp.
• Approximate energy expenditure of organs in human adults Organ Percentage of RMR
Liver 29 Brain 19 Heart 10 Kidney 7 Skeletal Muscle (at rest) 18 Remainder 17 Total 100
Factors Affecting RMR
Bod
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Bod
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Age
Sex
Hor
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Oth
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Basal metabolic rate
• The largest use of energy by the body. • BMR = the energy expended to maintain basic
physiological functions (e.g. heart beat, muscle contraction and function, respiration).
• BMR is the amount of energy expended while at rest in a neutrally temperate environment
• BMR is the minimum level of energy expended by the body to sustain life in the awake state.
How to measure BMR • BMR is the minimum amount of energy a body requires when lying in physiological
and mental rest • Subject fasted for 12 hours (post-absorptive
state, meaning the digestive system is inactive)
• Subject is awake, but rested physically and mentally in a thermoneutral, quiet environment, throughout the measurement. (not too hot or cold)
• Use direct calorimetry or indirect calorimetry. Note: If one of these conditions is not met (e.g. shorter time interval for fasting) the measurement is usually termed resting metabolic rate (RMR).
BMR or RMR?
• RMR = Resting Metabolic Rate • RMR is ≈ 3% higher than BMR, but it is
very difficult to measure BMR. • RMR is measured instead, and the two
terms and values are used interchangeably.
Measuring energy expenditure
• Doubly labelled water measurements • Respiratory quotient (RQ) or
respiratory coefficient
Estimating BMR • Several equations exist • The earliest: Harris-Benedict equation (1919)
Original Harris-Benedict (1919)
• where P is total heat production at complete rest, m is the weight, h is the stature (height), and a is the age, and with the difference in BMR for men and women being mainly due to differences in body weight.
Men
Women
Currently used formula
• Harris-Benedict estimation formula – males: RMR = 66.5 + (13.75 x wt) + (5 x ht) – (6.8 x age) – females: RMR = 655 + (9.6 x wt) + (1.8 x ht) – (4.7 x age)
• Mifflin-St. Jeor (1990) estimation formula – males: RMR = (9.99 x wt) + (6.25 x ht) – (4.92 x age) + 5 – females: RMR = (9.99 x wt) + (6.25 x ht) – (4.92 x age) – 161
Harris-Benedict equation – Males: BMR = 66.47 + (13.5 x wt) + (5 x ht) – (6.76 x age) – Females: BMR = 655.1 + (9.56 x wt) + (1.85 x ht) – (4.68 x age)
– wt = weight (kg), ht = height (cm), age (years)
– Total calorie need = BMR X activity factor X injury factor – Injury factor : 1.0 (no illness or non stress) – Activity factor or physical activity (PAL)
• Bed rest = 1.0 – 1.1 • Very light= 1.2 – 1.3 (sit, stand, drive, sew, iron, cook) • Light = 1.4 – 1.5 (house cleaning, child minding, golf) • Moderate = 1.6 – 1.7 (gardening, cycling, dancing, tennis) • Heavy = 1.8 – 2.1 (manual labour, climbing, soccer, basketball) • Strenuous = 2.2 – 2.4
Currently used formula • WHO/FAO/UNU (1985)
Males – 18-30 years (MJ/day) = 0.0640 W + 2.84 – 30-60 years (MJ/day) = 0.0485 W + 3.67 Females – 18-30 years (MJ/day) = 0.0615 W + 2.08 – 30-60 years (MJ/day) = 0.0364 W + 3.47
• Henry & Rees (1991) Males – 18-30 years (MJ/day) = 0.0560 W + 2.800 – 30-60 years (MJ/day) = 0.0460 W + 3.160 Females – 18-30 years (MJ/day) = 0.0480 W + 2.562 – 30-60 years (MJ/day) = 0.0480 W + 2.448
• Basal metabolic rate for Malaysians • The present study shows that the BMR in
adult Malaysian is lower than that predicted by the FAO/WHO/UNU(1985) and Henry and Rees (1991) equations and should not be dismissed as an artifact. There is a good reason to believe that the capacity to low down metabolism in a hot and humid climate experienced throughout the year as a genuine phenomenon in Malaysia besides body size and composition and metabolic economies in response to energy deficit.
Ismail et al., 1998
Physical activity
• Dependent on lifestyle: sedentary or physically active.
• Sedentary = 1.2 PAL • Active: ≈ 1.9 PAL
Metabolisable energy intake
• Each food item has a specific metabolisable energy intake.
• For a normal human this value is obtained by 85% of kcal or kJ in a food item
• = the amount of energy actually obtained by a human after the digestive processes have been completed.
Energy balance
• Remember Form 5 Physics? • The First Law of Thermodynamics? • That energy can be neither destroyed nor
created. • Therefore, EI = EE, body energy stores
must remain constant.
Energy Requirement (WHO 1985) • The energy requirement of an individual is the level of
energy intake from food that will balance energy expenditure
• when the individual has a body size and composition, and level of physical activity consistent with long-term good health
• and that will allow for the maintenance of economically necessary and socially desirable physical activity
• in children & pregnant or lactating women; the energy requirement includes the energy needs associated with the deposition of tissues or the secretion of milk at rates consistent with good health
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Energy balance • Refers to the relationship between energy in (food consumption)
and energy out (physical activity). – Positive balance – Negative balance
• Storing Fat as Energy • Historically, the body’s ability to store energy as fat was
extremely useful. • Fat stores are still important today, as they help us to
– Maintain body temperature – Build and maintain body tissue and cells – Protect internal organs – Fuel muscle movement
• Easy to over-consume food and store an excess of energy and have systematically reduced physical activity in our daily lives through all the conveniences available