Energy sources
Energy sources, uses, balance and its evaluation
Introduction
• energy sources: carbohydrate (4 kcal/g), fat/oil (9 kcal/g), protein (4 kcal/g), alcohol (7 kcal/g) o ethyl alcohol (ethanol, C2H5OH) not methyl alcohol (methanol, CH3OH), metabolised in the liver • energy intake is total metabolisable energy an individual obtains from food • Estimated Average Requirements (EAR) for energy:
about 50% should come from carbohydrates
no more than 35% should come from fat
about 15% should come from protein
Introduction • energy intake is regulated by several factors: o external: non-physiological (social, economic, food characteristics, psychological [appetite], environment, etc o internal: physiological needs [digestive factors, circulatory, CNS, hunger, etc] • hunger is the stimulus that drives our need to eat o signals are sent from empty stomach, small intestine, reduced nutrient levels in blood to hypothalamus; trigger feelings of “hunger” o we can override signals and habituate to delaying hunger response actions 3
Introduction
Introduction • appetite is another signal to eat sights, smells, thoughts or discussion of foods may stimulate appetite; stressful situations stimulate (or suppress) appetite
we can have appetite for food with or without hunger • satiety is the feeling of fullness that stops appetite and hunger signals • satiety signals originating in the stomach are delayed from the start of eating; it is easy to overeat before satiety signals are received and acted upon • length of time food stays in stomach and small intestine (e.g. fibre-rich meals) affects duration of satiety and initiation of hunger signals 5
Energy uses
Uses/expenditure I. Life-sustaining functions (Basal metabolism) e.g. breathing, producing heartbeats, maintaining body temperature and muscle tone, functioning of glands, cells, etc) II. Physical activity (Thermic effect of exercise) III. Biological processing of food (Thermic effect of food
Energy uses I. Life-sustaining functions (Basal metabolism) • accounts for 60-70% of total daily energy expenditure • amount of energy required to maintain them for a specified unit of time is called basal metabolic rate (BMR); it takes very specialised equipment and precise conditions to measure BMR • factors affecting basal energy needs; depend mainly on 1) how much lean body mass a person has i.e. muscles, which typically represents 35 – 40% of body weight and 2) whether the amount of that tissue is changing • certain internal organs are responsible for unequal amount of basal energy usage: e.g. liver and brain, accounting for only 4% of body weight but are responsible for 40% of BMR
7
Energy uses Factors affecting basal energy needs • Body composition (metabolically active tissues, ??) • Body condition (well-developed muscle tissues, ??) • Sex (women have 10-12% lower than men, ??) • Hormonal secretions (adrenal, thyroid glands, ??) • Age (changes in proportion of metabolically active tissues ??) • Pregnancy (6-9th month; high metabolic activity of foetus, placenta, maternal tissues or a combination, ??) • Undernutrition and overnutrition(??) • Body temperature (increases with increasing body temp., ??) • Environmental temperature (??) • Smoking (nicotine tends to increase BMR by approx. 10%, ??)
8
Energy uses II. Physical activity (Thermic effect of exercise) • second largest use of energy, account for 20 – 30% of total expenditure; manual labourer, serious athlete would use a higher proportion • you have very much control than basal metabolism • expenditure vary markedly from one day to the next; depend on type of activity (and intensity), duration of activity, your body weight
9
Energy uses i. Type of Activity: activity using larger amount of muscle mass uses more energy e.g. walking requires more energy than sitting and typing because more large muscles are involved in walking • intensity of an activity: running, even though involves many of the same muscle groups as walking, uses more energy per unit of time because the stride is longer and more frequent ii. Duration of Activity: the longer an activity is continued, the more energy will be used iii.Body Weight: the heavier a person is, the more energy he or she expends in moving that mass, i.e. for the same exercise at the same intensity for the same length of time, a heavier person expends more energy than a less heavy person 10
Energy uses Energy cost of some activities Activity Kcal/kg/min Activity Kcal/kg/min
Walking (3 mph) 0.039 Bicycling (racing) 0.127
Walking (3 mph, carrying 22 lb)
0.046 Bicycling (leisurely) 0.042
Walking (4 mph) 0.057 Cooking 0.015
Swimming (2 mph)
0.132 Running (5mins./mile)
0.269
Eating 0.007 Running (7mins./mile)
0.208
Football 0.112 Running (9mins./mile)
0.173
11
Energy uses III. Biological processing of food (Thermic effect of food, Specific dynamic effect) • energy is required for physiological processes of digestion, absorption, transport, storage of food and its nutrients i.e. body uses small amount of energy for processing food internally before you have access to larger amount of energy from food • these processes occur within six hours following a meal • accounts for 6 – 10% of total expenditure
12
28/11/2016
3
Energy balance • energy balance occurs when food energy content is matched by total amount of energy expended by the body • when energy intake exceeds energy expenditure, a state of positive energy balance occurs (e.g. overeating and inactivity during festivals, during pregnancy and lactation when the body purposefully increases energy stores) • when energy intake is lower than expenditure, a state of negative energy balance occurs (e.g. during starvation). Energy balance can be evaluated by assessing energy intake and energy expenditure 13
Energy balance • Weight loss strategies (diet, physical activity, lifestyle behaviour modification) • Weight gain strategies (diet, physical activity, lifestyle behaviour modification)
energy-regulating mechanisms that prevent/enhance weight gain involve complex, overlapping processes at the biochemical, endocrinology, neural, physiological and behavioural levels, all of which are interdependent
Energy balance
natural adaptation acquired through 1) evolution, allows the body to compensate for periods of over consumption or under consumption of energy in a way that maintains weight; 2) inherited, at least in part. Environmental factors may influence how effectively they operate
Energy evaluation
Energy intake assessment
Past intake (e.g. Diet recall [(24hr food recall), Diet History, Food frequency questionnaire) Present intake (e.g. Precise food weight records [ingredients, inedible materials], Weighed food records (direct weighing), Estimated food records (portion size, hh equipment)
Energy expenditure assessment Direct calorimetry (e.g. Calorimeter)as heat given off
Indirect calorimeter (e.g. Douglas technique, Ventilated hood respirometer) as oxygen used Non-calorimetry (e.g. Doubly labeled water technique, Heart rate monitoring, Activity Diary, Factorial methods)
Energy intake evaluation choice of dietary method depends on study objectives, time-scale, population characteristics, resources i. Document foods/meals consumed ii. Convert amounts of foods into nutrients food analysis (duplicate portions), food composition tables or nutrient databases i. Evaluate dietary intakes comparison with recommended intakes of nutrients and energy
Energy expenditure evaluation Direct calorimetry: determine energy use by measuring heat emanating from the body • subject is put into insulated chamber with a layer of water surrounding the chamber; • body heat released raises temperature of water layer; difference in temperature before and after is calculated and used to determine kcalories expended • less used due to complexity
Energy expenditure evaluation Indirect calorimetry: determine energy use by measuring Oxygen uptake, Carbon dioxide gas exhaled and standardised formulas to convert gas usage into kcalories • less costly than direct calorimetry
Introduction
• energy sources: carbohydrate (4 kcal/g), fat/oil (9 kcal/g), protein (4 kcal/g), alcohol (7 kcal/g) o ethyl alcohol (ethanol, C2H5OH) not methyl alcohol (methanol, CH3OH), metabolised in the liver • energy intake is total metabolisable energy an individual obtains from food • Estimated Average Requirements (EAR) for energy:
about 50% should come from carbohydrates
no more than 35% should come from fat
about 15% should come from protein
Introduction • energy intake is regulated by several factors: o external: non-physiological (social, economic, food characteristics, psychological [appetite], environment, etc o internal: physiological needs [digestive factors, circulatory, CNS, hunger, etc] • hunger is the stimulus that drives our need to eat o signals are sent from empty stomach, small intestine, reduced nutrient levels in blood to hypothalamus; trigger feelings of “hunger” o we can override signals and habituate to delaying hunger response actions 3
Introduction
Introduction • appetite is another signal to eat sights, smells, thoughts or discussion of foods may stimulate appetite; stressful situations stimulate (or suppress) appetite
we can have appetite for food with or without hunger • satiety is the feeling of fullness that stops appetite and hunger signals • satiety signals originating in the stomach are delayed from the start of eating; it is easy to overeat before satiety signals are received and acted upon • length of time food stays in stomach and small intestine (e.g. fibre-rich meals) affects duration of satiety and initiation of hunger signals 5
Energy uses
Uses/expenditure I. Life-sustaining functions (Basal metabolism) e.g. breathing, producing heartbeats, maintaining body temperature and muscle tone, functioning of glands, cells, etc) II. Physical activity (Thermic effect of exercise) III. Biological processing of food (Thermic effect of food
Energy uses I. Life-sustaining functions (Basal metabolism) • accounts for 60-70% of total daily energy expenditure • amount of energy required to maintain them for a specified unit of time is called basal metabolic rate (BMR); it takes very specialised equipment and precise conditions to measure BMR • factors affecting basal energy needs; depend mainly on 1) how much lean body mass a person has i.e. muscles, which typically represents 35 – 40% of body weight and 2) whether the amount of that tissue is changing • certain internal organs are responsible for unequal amount of basal energy usage: e.g. liver and brain, accounting for only 4% of body weight but are responsible for 40% of BMR
7
Energy uses Factors affecting basal energy needs • Body composition (metabolically active tissues, ??) • Body condition (well-developed muscle tissues, ??) • Sex (women have 10-12% lower than men, ??) • Hormonal secretions (adrenal, thyroid glands, ??) • Age (changes in proportion of metabolically active tissues ??) • Pregnancy (6-9th month; high metabolic activity of foetus, placenta, maternal tissues or a combination, ??) • Undernutrition and overnutrition(??) • Body temperature (increases with increasing body temp., ??) • Environmental temperature (??) • Smoking (nicotine tends to increase BMR by approx. 10%, ??)
8
Energy uses II. Physical activity (Thermic effect of exercise) • second largest use of energy, account for 20 – 30% of total expenditure; manual labourer, serious athlete would use a higher proportion • you have very much control than basal metabolism • expenditure vary markedly from one day to the next; depend on type of activity (and intensity), duration of activity, your body weight
9
Energy uses i. Type of Activity: activity using larger amount of muscle mass uses more energy e.g. walking requires more energy than sitting and typing because more large muscles are involved in walking • intensity of an activity: running, even though involves many of the same muscle groups as walking, uses more energy per unit of time because the stride is longer and more frequent ii. Duration of Activity: the longer an activity is continued, the more energy will be used iii.Body Weight: the heavier a person is, the more energy he or she expends in moving that mass, i.e. for the same exercise at the same intensity for the same length of time, a heavier person expends more energy than a less heavy person 10
Energy uses Energy cost of some activities Activity Kcal/kg/min Activity Kcal/kg/min
Walking (3 mph) 0.039 Bicycling (racing) 0.127
Walking (3 mph, carrying 22 lb)
0.046 Bicycling (leisurely) 0.042
Walking (4 mph) 0.057 Cooking 0.015
Swimming (2 mph)
0.132 Running (5mins./mile)
0.269
Eating 0.007 Running (7mins./mile)
0.208
Football 0.112 Running (9mins./mile)
0.173
11
Energy uses III. Biological processing of food (Thermic effect of food, Specific dynamic effect) • energy is required for physiological processes of digestion, absorption, transport, storage of food and its nutrients i.e. body uses small amount of energy for processing food internally before you have access to larger amount of energy from food • these processes occur within six hours following a meal • accounts for 6 – 10% of total expenditure
12
28/11/2016
3
Energy balance • energy balance occurs when food energy content is matched by total amount of energy expended by the body • when energy intake exceeds energy expenditure, a state of positive energy balance occurs (e.g. overeating and inactivity during festivals, during pregnancy and lactation when the body purposefully increases energy stores) • when energy intake is lower than expenditure, a state of negative energy balance occurs (e.g. during starvation). Energy balance can be evaluated by assessing energy intake and energy expenditure 13
Energy balance • Weight loss strategies (diet, physical activity, lifestyle behaviour modification) • Weight gain strategies (diet, physical activity, lifestyle behaviour modification)
energy-regulating mechanisms that prevent/enhance weight gain involve complex, overlapping processes at the biochemical, endocrinology, neural, physiological and behavioural levels, all of which are interdependent
Energy balance
natural adaptation acquired through 1) evolution, allows the body to compensate for periods of over consumption or under consumption of energy in a way that maintains weight; 2) inherited, at least in part. Environmental factors may influence how effectively they operate
Energy evaluation
Energy intake assessment
Past intake (e.g. Diet recall [(24hr food recall), Diet History, Food frequency questionnaire) Present intake (e.g. Precise food weight records [ingredients, inedible materials], Weighed food records (direct weighing), Estimated food records (portion size, hh equipment)
Energy expenditure assessment Direct calorimetry (e.g. Calorimeter)as heat given off
Indirect calorimeter (e.g. Douglas technique, Ventilated hood respirometer) as oxygen used Non-calorimetry (e.g. Doubly labeled water technique, Heart rate monitoring, Activity Diary, Factorial methods)
Energy intake evaluation choice of dietary method depends on study objectives, time-scale, population characteristics, resources i. Document foods/meals consumed ii. Convert amounts of foods into nutrients food analysis (duplicate portions), food composition tables or nutrient databases i. Evaluate dietary intakes comparison with recommended intakes of nutrients and energy
Energy expenditure evaluation Direct calorimetry: determine energy use by measuring heat emanating from the body • subject is put into insulated chamber with a layer of water surrounding the chamber; • body heat released raises temperature of water layer; difference in temperature before and after is calculated and used to determine kcalories expended • less used due to complexity
Energy expenditure evaluation Indirect calorimetry: determine energy use by measuring Oxygen uptake, Carbon dioxide gas exhaled and standardised formulas to convert gas usage into kcalories • less costly than direct calorimetry
Good
ReplyDeleteWell done
ReplyDeleteWell done
ReplyDeleteGood
ReplyDelete