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Questions and Answers
What proportion of daily energy expenditure is accounted for by basal metabolism?
What proportion of daily energy expenditure is accounted for by basal metabolism?
Which of the following is NOT a component of energy expenditure?
Which of the following is NOT a component of energy expenditure?
What primarily supports basal metabolic rate (BMR)?
What primarily supports basal metabolic rate (BMR)?
Which of the following conditions is likely to result in a lower BMR?
Which of the following conditions is likely to result in a lower BMR?
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Which component of thermogenesis is related to the energy expended for digestion and absorption of food?
Which component of thermogenesis is related to the energy expended for digestion and absorption of food?
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What term describes energy expended by the body to adapt to environmental changes?
What term describes energy expended by the body to adapt to environmental changes?
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How does body weight correlate with total energy expenditure?
How does body weight correlate with total energy expenditure?
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Which factor can cause BMR to vary between individuals?
Which factor can cause BMR to vary between individuals?
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What is adaptive thermogenesis primarily associated with?
What is adaptive thermogenesis primarily associated with?
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How does body composition affect Basal Metabolic Rate (BMR)?
How does body composition affect Basal Metabolic Rate (BMR)?
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Which factor is NOT included in energy equations for estimating energy needs?
Which factor is NOT included in energy equations for estimating energy needs?
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What occurs to BMR as individuals age?
What occurs to BMR as individuals age?
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During which of the following conditions is adaptive thermogenesis likely to occur?
During which of the following conditions is adaptive thermogenesis likely to occur?
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What percentage reduction in energy expenditure typically occurs per decade in aging adults?
What percentage reduction in energy expenditure typically occurs per decade in aging adults?
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Which of the following statements about women’s BMR is accurate?
Which of the following statements about women’s BMR is accurate?
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What role does physical activity play in energy expenditure calculations?
What role does physical activity play in energy expenditure calculations?
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What is the formula for calculating Basal Metabolic Rate (BMR)?
What is the formula for calculating Basal Metabolic Rate (BMR)?
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Which factor significantly influences the Thermic Effect of Food (TEF)?
Which factor significantly influences the Thermic Effect of Food (TEF)?
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How does the intensity of physical activity impact energy expenditure?
How does the intensity of physical activity impact energy expenditure?
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Which of the following is an estimate of the thermic effect of food for a 2000 kcal intake?
Which of the following is an estimate of the thermic effect of food for a 2000 kcal intake?
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What activity level should be multiplied by BMR for no physical activity?
What activity level should be multiplied by BMR for no physical activity?
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What is the impact of high-protein foods on the Thermic Effect of Food?
What is the impact of high-protein foods on the Thermic Effect of Food?
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Adaptively, what happens to metabolism during periods of overeating?
Adaptively, what happens to metabolism during periods of overeating?
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What is a characteristic of the Thermic Effect of Food that may be considered negligible in energy expenditure estimations?
What is a characteristic of the Thermic Effect of Food that may be considered negligible in energy expenditure estimations?
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Study Notes
Energy Balance and Body Composition
- Energy balance occurs when energy intake equals energy expenditure, resulting in stable weight.
- Weight gain occurs when energy intake exceeds expenditure.
- Weight loss occurs when energy expenditure exceeds intake.
- Body fat changes depend on daily energy balance.
- The 3500 Kcalorie Rule is traditionally 3500 kcalories of excess = 1 pound of fat gained.
- Significant fat energy reserves in healthy-weight adults range from 50,000 to 200,000 calories.
Energy Imbalance:
- Daily energy balance depends on energy in vs. energy out.
- Weight maintenance occurs when energy in equals energy out.
- Weight changes when this balance shifts.
Energy Imbalance: Fat Cell Enlargement
- Fat cells enlarge when a person eats too much energy-yielding nutrients (carbohydrates, fat, or protein).
Composition of Weight Changes
- Weight changes include fat, fluid, and lean tissue shifts.
- Rapid changes frequently involve water retention/loss (60% of adult body weight).
- Long-term weight changes involve 75% fat and 25% lean tissue during starvation; fat and lean losses are approximately equal.
Energy Balance Equation
- The simple energy in vs. energy out equation cannot fully explain obesity complexities.
- Metabolic changes play a significant role in weight management.
Energy in: The kCalories Foods Provide : Food Composition
- Foods and beverages contribute to energy in.
- Energy received from food depends on composition & consumed quantity.
- A bomb calorimeter measures kcalories in food by burning it and measuring released heat. This provides a measure of the food's energy value.
- The bomb calorimeter overstates the physiological fuel value, which is the energy actually derived by the human body.
- The body's metabolism is less efficient than a calorimeter, requiring corrections for accurate energy value tables.
- Energy values of foods can be calculated based on macronutrient content (carbohydrates, fats, proteins, and alcohol).
Bomb Calorimeter
- Used to measure energy content of foods.
- Burns food and measures heat released, providing a direct measure of food's energy value.
- Burning food releases heat, carbon dioxide, and water.
- Similar to how body cells metabolise nutrients. Chemical bonds break, forming CO2 and H2O.
- Oxygen consumption indirectly measures energy released. In body: Burning food breaks chemical bonds, combining carbon and hydrogen with oxygen. This produces carbon dioxide and water.
Physiological Fuel Value
- Bomb calorimeter overestimates energy available to the human body. The body is less efficient than a calorimeter in extracting energy from food.
- Cannot completely metabolise all energy-yielding nutrients.
- Researchers mathematically correct calorimeter measurements, creating tables with more accurate food energy values..
Energy in: The kCalories Foods Provide : Food intake
- Appetite plays a crucial role in regulating food intake, influencing when and how much a person eats.
- The decision to eat or not eat is not solely based on hunger.
- The body uses various signals to determine when to start and stop eating. These signals are influenced by environmental factors and genetic predispositions.
Food Intake: Hunger
- People eat primarily due to hunger, a physiological response to food needs.
- Hunger is triggered by nerve signals and chemical messengers in the hypothalamus.
- Hunger is influenced by nutrients in the bloodstream, previous meal, meal size/composition, eating patterns, climate, physical activity, hormones, and illness.
- Hunger determines what to eat, when to eat, and how much to eat.
- The stomach typically prompts eating roughly every 4 hours after a meal when empty or nearly empty.
Food intake : Satiation, Satiety
- Satiation occurs during a meal as food enters the GI tract, decreasing hunger.
- Triggered by stomach stretching, hormones (e.g., cholecystokinin) are released signaling to stop eating.
- Satiety continues after a meal to suppress hunger, preventing eating again for a while.
Overriding Hunger and Satiety
- Eating can be triggered by emotions like boredom or anxiety, as well as food cravings related to various stressors.
- Chronic stress relief through food consumption can lead to overeating and weight gain.
- External cues like time of day and food availability can stimulate eating. Cognitive factors (perceptions, and social interactions) also influence eating.
Sustaining Satiation and Satiety
- The nutrient composition of a meal affects satiation and its sustainability.
- Protein is the most satiating macronutrient while sugary drinks increase appetite.
- Foods low in energy density (e.g., high-fiber foods) are more satisfying and help control hunger.
- Fat has a weak effect on satiation but a strong effect on satiety; high-fat foods can lead to overconsumption due to their energy density and flavors.
- Portion size and satiety are directly correlated. Large portions of low-fat, high-fiber, low-energy-density foods are satisfying.
- Protein consumption satiates and reduces subsequent energy intake. Fructose in sugary drinks can stimulate appetite and increase food intake. High-fiber foods promote satiation by filling the stomach and delaying nutrient absorption.
Food Intake: Message Central—The Hypothalamus
- Eating behavior is complex, influenced by genetics, psychology, social, metabolic, and physiological factors.
- The hypothalamus is the central control center for eating, integrating signals related to energy intake, expenditure, and storage from various brain regions, GI tract and liver.
Gastrointestinal Hormones
- Numerous hormones affect appetite control and energy balance. Understanding these actions could lead to anti-obesity treatments.
- Neuropeptide Y challenges our understanding of eating behavior. It triggers carbohydrate cravings, initiates eating, decreases energy expenditure, increases fat storage, and promotes positive energy balance and weight gain.
Energy Out: The kCalories the Body Expends
- Heat is released when the body breaks down carbohydrates, fats, or proteins to generate energy and when that energy is utilized for work.
- The process of heat generation is called thermogenesis. It can be measured to assess energy expenditure.
- Total energy expenditure categorizes into: 1. basal metabolism, 2. physical activity, 3. thermic effect of food, 4. adaptive thermogenesis.
Components of Energy Expenditure 1-Basal Metabolism
- Basal metabolism accounts for about two-thirds of daily energy expenditure, supporting basic life functions and metabolic activities.
- Metabolic activities include: lung function, bone marrow, heartbeat, and kidney filtering.
- Basal metabolic rate (BMR) is the rate of energy expenditure for these life-sustaining activities.
- BMR varies between individuals and is influenced by factors such as age, growth, fever, stressors, environmental temperature, fasting/starvation, malnutrition, hormones, smoking, caffeine, and sleep.
- Resting metabolic rate (RMR) is similar to BMR but with less stringent criteria, so it is slightly elevated.
Components of Energy Expenditure 2-Physical activity
- Physical activity is the most variable and changeable component of energy expenditure, significantly influencing weight gain and loss.
- Energy needs during physical activity depend on factors like muscle mass, body weight, activity type, duration, frequency, and intensity.
Components of Energy Expenditure 3- Thermic effect of Food
- The thermic effect of food (TEF) is the energy required to process food—digestion, absorption, transport, metabolism, and storage of nutrients.
- Proportionate to food energy intake.
- Typically estimated at 10% of energy intake.
- Factors influencing TEF include various foods, meal size & frequency, high protein vs high fat foods.
Components of Energy Expenditure 4- Adaptive Thermogenesis
- Adaptive thermogenesis is the additional energy expended when the body is challenged by dramatic changes (physical conditions, exposure to extreme cold, overfeeding, starvation, trauma , etc.).
- The body works to build tissues, produce enzymes, and hormones.
- Energy expenditure from thermogenesis can be considerable, especially in certain acute scenarios like burn victims but is usually not calculated for healthy individuals due to variation and individual specificity.
Estimating Energy Requirements
- Factors influencing basal metabolic rate (BMR) and energy expenditure include gender, growth, age and physical activity.
- Women generally have lower BMR than men due to less lean body mass.
- BMR is higher during growth spurts (pregnant/ lactating women, infants, children, adolescents) and declines in adults due to reduced lean body mass, hormonal changes, and reduced physical activity related to age.
- Ongoing physical activity can help mitigate age-related declines in BMR.
- Energy equations to estimate energy requirements include factors for gender, growth, age, physical activity, body size.
- Even similar individuals can have different energy requirements due to genetic factors. Energy needs vary between individuals based on gender, growth, age, physical activity, and body size and composition.
Body Weight and Body Composition
- Distinction between body weight and body composition:
- Body weight is the total mass of a person's body.
- Body composition refers to the proportions of fat and lean tissues (muscles, organs, bones, and water).
- Direct measurement of body composition is not feasible in humans, indirect assessments include equations ( Body Weight = Fat + Lean Tissue).
- Weight alone does not indicate body composition changes. Gains/losses in weight do not reflect fat vs. lean tissue changes.
- People often incorrectly rely on just weight to measure their "fatness".
Body Fat and Its Distribution
- Weight alone doesn't fully indicate fat amount/distribution.
- The ideal body fat percentage varies depending on the individual. Lower body fat is often preferred in athletes, but this may vary. Higher fat percentages may be beneficial in certain circumstances, like pregnancies or extreme cold.
- The location of fat is crucial for health risks. Visceral fat increases health risks more than subcutaneous fat.
- Waist circumference is an effective indicator of visceral (abdominal) fat and associated health risks.
Body Fat and Its Distribution: Other Measures of Body Composition (e.g., BMI, Waist Circumference).
- Other techniques to assess body composition include BMI, waist circumference, and others. BMI is simple but does not measure body composition (fat vs lean tissue) alone. More precise techniques like Total body water analysis and near-infrared spectrophotometry exist, each with their own advantages/disadvantages.
Health Risks Associated with Body Weight and Body Fat
- Health risks are associated with both very low and very high body fat percentages. The ideal BMI is between 18.5 and 24.9.
- High BMI, especially central obesity, elevates the risk of cardiovascular disease, type 2 diabetes, chronic inflammatory diseases, etc.
- Too low BMI also poses various health risks.
- Relationships between body weight, body fat, and health risks, including cardiovascular disease, type 2 diabetes, inflammation, and cancer.
Nutrition in Practice: Eating Disorders
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Anorexia Nervosa: An eating disorder characterized by a refusal to maintain a minimally normal body weight and distortion of body image.
- Signs include chronic low calorie intake and a fear of weight gain.
- Characterized by an awareness of undernourishment, but a denial of the need for treatment along with various physical implications.
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Bulimia Nervosa: An eating disorder marked by repeated binge eating episodes, followed by self-induced purging including vomiting; misuse of laxatives/diuretics or excessive exercise.
- Characterized by distorted body image and frequent fluctuations in weight.
- Binge eating and subsequent purging are frequently present.
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Description
Test your understanding of energy balance and body composition. This quiz covers essential concepts such as weight maintenance, weight gain, and the effects of energy intake on body fat. Explore the significance of the 3500 Kcalorie rule and its implications for weight changes.
