Chapter 6: Energy 1. Energy Balance - Introduction 2 Energy metabolism deals with change and...
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Transcript of Chapter 6: Energy 1. Energy Balance - Introduction 2 Energy metabolism deals with change and...
Chapter 6: Energy1
Energy Balance - Introduction2
Energy metabolism deals with change and balance. Our bodies constantly convert fuel energy from food into the energy used at work, play, and rest.
Fuel is “burned” and stored as necessary
to provide a continuous flow of energy for the body’s work
Energy Balance3
Key concepts Food energy is changed into body energy
to do work The body uses most of its energy intake
for basal metabolic work needs A balance between intake of food energy
and output of body-work energy maintains life and health
States of being underweight and overweight reflect degrees of body energy imbalance
Objectives4
Identify the human energy system
Identify the human energy balance
Identify the human energy requirements
Human Energy System5
Basic energy needs – Body needs constant energy to do the work necessary to maintain life and health
Voluntary work and exercise –includes all physical actions related to a person’s usual activities, as well as any additional activities
Involuntary body work – all activities of the body that are not consciously performed - such as digestion, circulation, respiration, and absorption
- Referred to as the “thermic effect of food”
Human Energy System/Basic Energy Needs
6
The body requires energy in various forms:Chemical energy: in many metabolic processesElectrical energy: in brain and nerve activitiesMechanical energy: in muscle contractionThermal energy: to keep the body warm
Sources of fuel- fuel is provided in the form of nutrients3 energy nutrients: Carbohydrates
(primary), fat (secondary) and protein (last resort)
Types of energy7
Measurement of energy8
Unit of measure: calorie or kilocalorieIn common usage:
an amount of energy in food or expended in physical actions
In Nutritional Science: Kilocalorie – the large caloric unit
1000 calories = Kcal or Kcalorie- the amount of heat necessary to raise 1 kg
of water 1 degree centigrade- “Joule” is the international measurement of energy
Measurement of Energy 9
Energy-yielding nutrients have “basic fuel factors”Basic fuel factors reflect the relative fuel
densities:Density:
refers to the degree of concentrated material in a given substance. More material in a smaller amount of substance gives that substance a greater density.
Caloric Density: higher concentration of energy (kcals) in a smaller amount of food.Foods high in fat have the highest caloric
density
Caloric density due to fat10
Measurement of Energy11
Nutrient Density: concentration of all nutrients in a given amount of food
Relative fuel densities:CHO: 4kcal/gFat: 9 kcal/gProtein: 4 kcal/gAlcohol: 7 kcal/g
12
Energy Balance13
Two energy systems:External energy cycle – In the environment, the
ultimate source of energy is the sun. Using water and carbon dioxide as raw material, plants transform the sun’s radiation into stored chemical energy -> mainly CHO
Internal energy cycle – When humans eat plants and animals, the stored energy is changed into body fuel, glucose and fatty acids and cycles them into various energy forms to serve the body’s needs
Energy Balance14
Overall energy balance within the human body depends on the energy intake in relation to energy output.
3 energy-yielding nutrients in food:CarbohydratesFatsProteins
Energy Intake15
Sources of Stored EnergyGlycogen – 12- 48 hour reserve of glycogen
exist in liver and musclesAdipose Tissue – Fat storage is larger than
glycogenMuscle Mass – Limited supply stored in
muscle mass, lean muscle must be maintained for health.Only during longer periods of fasting or
starvation does the body turn to this tissue for energy
Energy Output16
The necessary activities to sustain life – i.e. normal body functions, regulation of temperature, tissue growth and repair - use energy from food and body reserves
Three demands for energy determine the body’s total energy requirements: Resting energy expenditure Physical activity Thermal effect of food
Temperature regulation17
Energy Output18
Resting Energy Expenditure (REE)= RMR (Resting Metabolic Rate)
*The sum of all internal working activities of the body at rest*Expressed as kcal/day
Amount of Kcal needed to consume over 24 hours to maintain current weight while at rest – often called Basal Energy Expenditure (BEE)
Resting energy expenditure19
Energy Output20
Also known as “Basal Metabolic Rate” –BMRMeasures resting
energy expenditure or basal metabolic rate
Thyroid test often are used to indicated BMR – measures the thyroid gland and the blood levels of the hormone thyroxine
Energy Output21
Calculating Basal Energy Needs Men: 1 kcal x kg
body wt. x 24 hrs Women: 0.9 kcal x
kg body wt. x 24 hrs
Factors influencing BMR22
Lean body mass – There is increased metabolic activity in lean tissue (muscle and tissue) as compared to fat and bone
Growth periods – Growth hormone stimulate cell metabolism and raises BMR 15 % - 20 % - also raises in pregnancy requiring 300 kcal/day extra
Body temperature – Fever increases BMR 7 % per each degree F rise in temperature (.83 Degree C)
Hormonal status – Depending of hormone secretion BMR will rise or fall Thyroid ---Hyper vs Hypo
Physical Activity23
Energy expenditure for physical activity goes above and beyond energy used for resting energy needs
Energy output during physical activity varies widely across individuals
Thermal Effect of Food24
After eating, food stimulates metabolism
Requires extra energy for digestion, absorption, and transport of the nutrients to the cells
5-10% of the body’s total energy needs for metabolism relates to the processing of food
Total Energy Requirement25
Resting energy expenditure (REE) + physical activity + thermic effect of food
To maintain daily energy balance:Food-energy intake =
body-energy outputIntake > output = weight
gain (extreme: obesity)Intake < output = weight
loss (extreme: anorexia)
Total Energy Requirement26
Graph of total energy expenditure
Recommendations for Dietary Energy Intake
27
General life cycle:Growth periods – chart page 88 (Table 6 – 3)Extra energy per unity of body weight is
necessary to build new tissue – e.g. infancy, adolescence, pregnancy
Adulthood – energy needs level offAging – energy needs decline
30-40 decrease by 3 %40-50 decrease by 3 %50-60 decrease by 7.5 %60-70 decrease by 7.5 %70-80 decrease by 10%
Energy needs in the life cycle28
Recommendations29
Dietary Reference Intakes (DRIs)Food and Nutrition Board of the Institute of Medicine
created recommendation for energy intake based on gender, age, and other considerations
Refer to chart page 89 (Table 6 – 5)
Dietary Guidelines for Americans indicate energy needs based on two recommendations:Maintain ideal weightTo prevent gradual weight gain over time, make
small decreases in food and beverage calories and increase physical activity
Adopt a balanced eating pattern
Recommendations30
MyPlate2011 graphic guideline
MyPyramid: Can outline an individualized calorie
level and corresponding serving sizesCan provide helpful information re:
Maintaining balance between food intake and energy output through physical activity
Recommendations31