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Questions and Answers
What percentage of the body is primarily composed of water in adults?
What percentage of the body is primarily composed of water in adults?
How many kilocalories are derived from 6 kg of protein in muscle tissue?
How many kilocalories are derived from 6 kg of protein in muscle tissue?
Which hormone is primarily involved in influencing energy expenditure?
Which hormone is primarily involved in influencing energy expenditure?
What happens to hepatic glucose production during a negative energy balance?
What happens to hepatic glucose production during a negative energy balance?
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What is a primary function of leptin in the body?
What is a primary function of leptin in the body?
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What is one possible consequence of growth factor alterations during starvation?
What is one possible consequence of growth factor alterations during starvation?
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What is a common cause of death in laboratory mice that may not apply to humans?
What is a common cause of death in laboratory mice that may not apply to humans?
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How does calorie restriction (CR) potentially influence cellular aging?
How does calorie restriction (CR) potentially influence cellular aging?
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In the hierarchy of fuel selection in humans, which macronutrient is prioritized for oxidation when both carbohydrates and fats are present?
In the hierarchy of fuel selection in humans, which macronutrient is prioritized for oxidation when both carbohydrates and fats are present?
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What may be a limitation in extrapolating findings from caloric restriction in mice to humans?
What may be a limitation in extrapolating findings from caloric restriction in mice to humans?
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What is one difficulty that humans face regarding caloric intake over their lifetime?
What is one difficulty that humans face regarding caloric intake over their lifetime?
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Which of the following effects of calorie insufficiency is not proven?
Which of the following effects of calorie insufficiency is not proven?
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Which mechanism is associated with calorie restriction's potential effect on longevity?
Which mechanism is associated with calorie restriction's potential effect on longevity?
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What is considered the most accurate index of general nutritional status?
What is considered the most accurate index of general nutritional status?
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What is the main purpose of measuring muscle mass in the context of stunting tests?
What is the main purpose of measuring muscle mass in the context of stunting tests?
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Which method is NOT mentioned as reliable for measuring total-body skeletal muscle mass?
Which method is NOT mentioned as reliable for measuring total-body skeletal muscle mass?
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How does calorie restriction primarily affect lifespan?
How does calorie restriction primarily affect lifespan?
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What effect does a 40% calorie restriction have on the lifespan of mice?
What effect does a 40% calorie restriction have on the lifespan of mice?
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Which of the following is a potential benefit of calorie restriction?
Which of the following is a potential benefit of calorie restriction?
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What percentage reduction in caloric intake defines calorie restriction?
What percentage reduction in caloric intake defines calorie restriction?
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What is the role of D3-creatine in measuring muscle mass?
What is the role of D3-creatine in measuring muscle mass?
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What is the primary objective of using blood doping or erythropoietin in athletes?
What is the primary objective of using blood doping or erythropoietin in athletes?
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Which of the following methods is considered legitimate for increasing one's blood oxygen levels?
Which of the following methods is considered legitimate for increasing one's blood oxygen levels?
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What is a significant consequence of blood doping in young athletes?
What is a significant consequence of blood doping in young athletes?
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Which performance-enhancing agent is commonly used by power athletes but has unclear effects on power activity?
Which performance-enhancing agent is commonly used by power athletes but has unclear effects on power activity?
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What is a notable medical application of erythropoietin?
What is a notable medical application of erythropoietin?
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How much energy do fats and oils provide per gram?
How much energy do fats and oils provide per gram?
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What happens to triglycerides in adipose tissue during fasting?
What happens to triglycerides in adipose tissue during fasting?
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What percentage of the American diet is composed of energy derived from triglycerides and other lipids?
What percentage of the American diet is composed of energy derived from triglycerides and other lipids?
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What is the estimated risk of developing T2D if both parents have the condition and the individual becomes obese?
What is the estimated risk of developing T2D if both parents have the condition and the individual becomes obese?
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Which of the following represents an important consideration in strength training regimens for optimal muscle gains?
Which of the following represents an important consideration in strength training regimens for optimal muscle gains?
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What is the role of insulin in muscle anabolism?
What is the role of insulin in muscle anabolism?
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Which factor is believed to potentially increase muscle catabolism?
Which factor is believed to potentially increase muscle catabolism?
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What type of exercise is most effective in increasing aerobic capacity?
What type of exercise is most effective in increasing aerobic capacity?
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Which of the following hormones has a dose-response relationship that increases muscle anabolism?
Which of the following hormones has a dose-response relationship that increases muscle anabolism?
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How does high altitude training affect physical performance?
How does high altitude training affect physical performance?
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What is one potential effect of glucocorticoids on muscle tissue?
What is one potential effect of glucocorticoids on muscle tissue?
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What is the primary effect of caffeine on exercise performance?
What is the primary effect of caffeine on exercise performance?
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Which physiological parameter does VO2max primarily depend on in endurance athletes?
Which physiological parameter does VO2max primarily depend on in endurance athletes?
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What is the purpose of blood doping in athletic performance?
What is the purpose of blood doping in athletic performance?
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What is a major side effect associated with creatine supplementation?
What is a major side effect associated with creatine supplementation?
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What role does carbohydrates (CHO) play in relation to creatine?
What role does carbohydrates (CHO) play in relation to creatine?
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Which aspect of exercise performance does creatine supplementation improve?
Which aspect of exercise performance does creatine supplementation improve?
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What is the composition of creatine stored in muscle?
What is the composition of creatine stored in muscle?
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What is considered a performance-enhancing level of caffeine intake?
What is considered a performance-enhancing level of caffeine intake?
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Study Notes
Adaptations to Starvation
- Body composition is mostly water (~60-70% in children, ~50% in adults).
- Lean tissue (muscle) is ~20% protein.
- Most body energy is stored as triglycerides (fat) in adipose tissue.
- Total energy content of fat in body is approximately 135,000 kcal for a 70 kg individual.
Lean Tissue Conservation
- Normal protein loss equals protein intake in a healthy individual.
- Protein loss of ~500g lean tissue/100g protein lost.
- 15 kg loss of lean mass can be life-threatening, ~30 days or less is the maximum time a person can survive under starvation.
- Reducing nitrogen loss is crucial as people can go longer without food if nitrogen losses are reduced.
Sequential Metabolic Response to Prolonged Fasting
- Phase 1: Glycogen depletion, high nitrogen loss, baseline fuel mixture maintained.
- Phase 2: Fatty acid oxidation, ketones, reduced nitrogen and tissue loss, 7 days.
- Phase 3: Brain keto-adaptation, reduced nitrogen and tissue loss, further adaptations by kidneys and endocrine system, 7+ days.
Role of Different Tissues in Starvation
- Liver: Glycogen depletion, reduced glucose release, increased fatty acid oxidation, reduced gluconeogenesis.
- Pancreas: Reduced insulin secretion.
- Adipose: Increased fatty acid release.
- Muscle: Reduced glucose oxidation, increased fat oxidation, reduced protein breakdown.
- Brain: Keto-adaptation, reduced glucose oxidation, reduced amino acid use for gluconeogenesis.
Other Information
- Loss of 40-50% of lean body mass is typically lethal, with loss of ~15 kg being life-threatening.
- People may survive 60-90 days without food, depending on hydration and electrolyte maintenance.
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Description
This quiz explores the physiological adaptations the body undergoes during starvation, including body composition and metabolic responses. It examines the conservation of lean tissue and the sequential phases of metabolic response to prolonged fasting. Test your knowledge on how the body copes and survives under such conditions.
