1. Williams' Basic Nutrition & Diet Therapy
Chapter 6
Energy Balance
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2. Human Energy System Basic energy needs
Voluntary work: conscious activities of daily living
Involuntary body work will carried out by metabolically active systems such as the heart, muscles, and gastrointestinal: greatest share of energy output
Circulation
Respiration
Digestion
Absorption
Explain that because the body needs constant energy, without storage of energy we would need to be eating constantly.
List some common voluntary activities with the students’ help.
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3. Human Energy System
Involuntary body work Chemical energy: many metabolic processes
Electrical energy: brain and nerve activities
Mechanical energy: muscle contraction
Thermal energy: to maintain body temperature
Ask the students to remember what they learned about the digestive system. What are some involuntary movements made after swallowing food?
Provide examples of body systems involved in each type of energy.
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4. Sources of Fuel Provided in the form of ATP
Carbohydrate: primary source of fuel
Fat
Protein
To maintain health, the average daily food energy intake should equal the daily body energy needs.
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5. Measurement of Energy Calorie is the term in common usage
Kilocalorie (1000 calories) is used in nutrition science
Amount of heat needed to raise 1 kg of water 1° C
Abbreviated as kcalorie or kcal
Joule (J): international unit
Convert kcal to kJ: multiply kcal by 4.184
Ask the class to explain the difference between calorie and Calorie in their own words.
The joule is used internationally as the unit of energy measurement.
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6. Food Energy: Fuel Factors
Carbohydrate: 4 kcal/g
Fat: 9 kcal/g
Protein: 4 kcal/g
Alcohol: 7 kcal/g
Explain why fat is the best storage form of energy. Mention the caloric density of fat and that if the body’s major form of energy storage were protein or carbohydrate, it would take a much larger space to store the same amount of energy.
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7. Caloric and Nutrient Density
Density: degree of concentration of material in a given substance
Caloric density: high concentration of energy in a small amount of food
Fats have highest caloric density
Nutrient density: relative concentration of nutrients (e.g., vitamins and minerals)
Food guides recommend foods that are nutrient-dense such as nuts, avocados, cheese, and nut butters
To help students understand density, use the example of a box full of feathers next to a box full of marbles. Both boxes are the same size, but one is more dense than the other.
Explain that density can be both good and bad. Nutrient-dense foods are usually better than calorie-dense foods, although a food may be both.
List examples of nutrient-dense and calorie-dense foods.
Ask students to consider the nutrient density of the foods they ate at breakfast. Is their diet balanced among the various nutrients?
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8. Energy Balance Two energy systems support human life
External energy cycle: plants transform radiation from the sun into stored chemical energy (carbohydrates, proteins, and fats)
Internal energy cycle: animals, including human beings, use the stored chemical energy for body needs, therefore energy is being lost from the body as heat
Explain why these are called “cycles.” Mention water, carbon dioxide, and heat energy.
Ask the students to explain the difference between external energy and internal energy.
Explain that energy is stored in the bonds of nutrients.
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9. Energy Intake Energy intake
The body’s energy balance depends on energy intake in relation to energy output
Main source of energy is food, supplemented by energy stored in body tissues
Stored energy is used when food is not available.
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10. Sources of Food Energy Sources of food energy
Carbohydrates, protein, and fat
Energy intake can be computed by tracking intake and calculating its energy value
Nutritrac on Evolve is an excellent tool for calculating energy intake
ChooseMyPlate is another free software tool for calculating energy intake
Ask students to think about their energy intake over the last 24 hours. How many think they are in energy balance?
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11. Sources of Stored Energy
Glycogen: 12- to 48-hour store in liver and muscles
Adipose tissue: varies by individual, most concentrated form of energy
Muscle mass: used only during longer periods of fasting or starvation
How does the body supply energy during sleep? (Glycogen stored in the liver and muscles maintains normal blood glucose levels during sleep.)
Where in the body is glycogen stored? (Liver and muscles)
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12. Energy Output Metabolism: chemical changes that occur during:
Normal body functions
Regulation of body temperature
Tissue growth and repair
Total energy demands determined by:
Resting energy expenditure
Physical activity
Thermic effect of food
Chemical changes occurring during these activities are called metabolism.
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13. Resting Energy Expenditure
Sum of all working internal activities of the body-higher than basal energy expenditure due to all the internal working activities of the body
Expressed in kilocalories per day
Also called resting metabolic rate (RMR), basal energy expenditure (BEE)
The TEF also is the energy required during digestion.
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14. Energy Output Measuring basal metabolic rate or resting metabolic rate
Sometimes done in clinical practice
Uses indirect calorimetry to measure
Measures exchange of carbon dioxide
What is indirect calorimetry? (Measurement of the amount of energy a person uses at rest)
Where is indirect calorimetry usually performed? (The subject breathes into a mouthpiece or ventilated hood system while lying down.)
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15. Energy Output
A metabolic cart is used to measure RMR.
Alternative methods for measuring RMR have been developed using fast, portable devices.
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16. Predicting Basal Metabolic Rate
Multiply 0.9 or 1 kcal/kg body weight by 24 (hours in a day)
Other measures are available
Mifflin-St. Jeor equation found to give most reliable RMR
Ask students to estimate their body weight in kilograms. Have them calculate their RMR (also called BMR).
Mention alternative formulas used to calculate RMR.
Have students calculate RMR according to the Mifflin-St. Jeor equation. Is the result similar to that obtained with the formula depicted on the slide?
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17. Predicting Basal Metabolic Rate
Thyroid function tests also can be used
Thyroid hormone regulates metabolism
Thyroxine controls basal metabolic rate
Explain the relation of iodine to thyroxine and how this hormone affects metabolism.
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18. Factors That Influence Basal Metabolic Rate
Lean body mass: greater metabolic activity in lean tissues
Growth periods: growth hormone stimulates cell metabolism and raises BMR
Body temperature: fever increases BMR 7% for each 1°F rise in temperature
Hormonal status: example: hypothyroidism decreases BMR
What percentage of BMR is raised by the growth hormone? (15% to 20%)
A patient has a fever of 100° F. How much of an increase in BMR occurs? (Fever increases BMR 7% for each 1° F rise in temperature.)
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19. Physical Activity Physical activity will increase energy expenditure
Exercise reduces risk of many diseases, improves quality of life
Energy expenditure can be estimated by categorizing activity and multiplying RMR by category factor (1.0 to 2.5)
Representative kilocalorie expenditures of different types of physical activities are presented in Table 6-1 in the text.
How can a person increase energy expenditure to lose weight? (Increase physical activity, build lean muscle mass)
What physical activities have high energy expenditure values? (Aerobics, cycling, running, fast walking, weight training)
Explain that the side effects of emotional stress—muscle tension, restlessness, and agitated movements—might increase energy expenditure, but only slightly.
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20. Thermic Effect of Food
Takes place when food is eaten and energy is required to:
Digestion
Absorption
Transportation of nutrients to cells
Explain that even though it does take energy to digest, absorb, and transport food, no food produces a negative energy balance. All foods provide energy, including celery and cabbage (two of the more famous foods for weight loss), even if the kilocalories are quite low.
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21. Total Energy Requirement
Total energy requirement made up of:
BMR + physical activity + TEF
To maintain daily energy balance:
Food energy intake = body energy output
Intake > output = Weight gain (extreme: obesity)
Intake < output = Weight loss (extreme: anorexia)
If a woman weighs 150 lbs (68 kg), eats 2500 kcal/day, and does not exercise, will she gain or lose weight? (She will gain weight. [energy expenditure = 2307 while kcal intake = 2500]).
Explain that the term anorexia used here is a clinical term and not the same as anorexia nervosa, the eating disorder.
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22. Total Energy Requirement
Use Clinical Applications box, “Evaluate Your Daily Energy Requirements”
Record food and activities for a day
Calculate energy intake (kilocalories) and output (kilocalorie expenditure)
Use Table 6-1 to find the category of the activity and the kcal/lb/hr used.
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23. Recommendations for Dietary Energy Intake
General life cycle
Growth periods
Extra energy needed to build new tissues
Greatest growth is infancy through adolescence
Pregnancy and lactation also require increased energy intake
Talk about the extra calories needed during pregnancy and lactation and why this occurs. Ask the class how many more calories, on average, a pregnant woman needs.
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24. General Life Cycle Adulthood
Energy needs plateau as full growth achieved
BMR then declines 1% to 2% per decade, reducing energy needs; therefore food choices should reflect a decline in caloric density and a greater emphasis on nutrient density
Rapid decline occurs at age 40 (men) and 50 (women)
Explain why caloric adjustments must be made in the older adult years.
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25. Dietary Reference Intakes
Use Table 6-4
Note average weight, height, BMI, and PAL for each group
Ask students to identify where they fit on the Food and Nutrition Board recommendations.
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26. Dietary Guidelines for Americans
Prevent/reduce overweight/obesity through improved eating and physical activity
Control calorie intake to manage body weight
Increase physical activity and reduce sedentary activities
Adjust calorie balance to stage of life
Select eating pattern that meets nutrient needs over time
Explain that weight gain is gradual. To combat this increase, small decreases in energy intake must take place.
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27. Choose MyPlate Web site: www.choosemyplate.gov
Determine calorie level and serving sizes from each good group
Based on age, gender, weight, height, activity level
The site also explains how to use physical activity to maintain energy balance.
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