Adaptations to Starvation
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Questions and Answers

What percentage of the body is primarily composed of water in adults?

  • 50% (correct)
  • 40%
  • 60-70%
  • 30%

How many kilocalories are derived from 6 kg of protein in muscle tissue?

  • 600 kcal
  • 2400 kcal (correct)
  • 3200 kcal
  • 1800 kcal

Which hormone is primarily involved in influencing energy expenditure?

  • Insulin
  • Ephedrine
  • Thyroid hormones (T4/T3) (correct)
  • Leptin

What happens to hepatic glucose production during a negative energy balance?

<p>It reduces (A)</p> Signup and view all the answers

What is a primary function of leptin in the body?

<p>To inform the brain to produce estrogen (A)</p> Signup and view all the answers

What is one possible consequence of growth factor alterations during starvation?

<p>Reduced reproductive function (C)</p> Signup and view all the answers

What is a common cause of death in laboratory mice that may not apply to humans?

<p>Cancer (B)</p> Signup and view all the answers

How does calorie restriction (CR) potentially influence cellular aging?

<p>By reducing hormones influencing aging (B)</p> Signup and view all the answers

In the hierarchy of fuel selection in humans, which macronutrient is prioritized for oxidation when both carbohydrates and fats are present?

<p>Simple sugars (D)</p> Signup and view all the answers

What may be a limitation in extrapolating findings from caloric restriction in mice to humans?

<p>Findings may not reflect differences in cancer mortality (C)</p> Signup and view all the answers

What is one difficulty that humans face regarding caloric intake over their lifetime?

<p>Maintaining a consistent calorie deficit (B)</p> Signup and view all the answers

Which of the following effects of calorie insufficiency is not proven?

<p>Increased apoptosis in cells (C)</p> Signup and view all the answers

Which mechanism is associated with calorie restriction's potential effect on longevity?

<p>Reduced cell division (B)</p> Signup and view all the answers

What is considered the most accurate index of general nutritional status?

<p>Muscle mass (C)</p> Signup and view all the answers

What is the main purpose of measuring muscle mass in the context of stunting tests?

<p>To determine general nutritional status (A)</p> Signup and view all the answers

Which method is NOT mentioned as reliable for measuring total-body skeletal muscle mass?

<p>Ultrasound (D)</p> Signup and view all the answers

How does calorie restriction primarily affect lifespan?

<p>By reducing caloric intake without malnutrition (D)</p> Signup and view all the answers

What effect does a 40% calorie restriction have on the lifespan of mice?

<p>Extends lifespan by approximately 20% (B)</p> Signup and view all the answers

Which of the following is a potential benefit of calorie restriction?

<p>Decreased age-related diseases (B)</p> Signup and view all the answers

What percentage reduction in caloric intake defines calorie restriction?

<p>20-40% (D)</p> Signup and view all the answers

What is the role of D3-creatine in measuring muscle mass?

<p>To assess creatine pool size in muscle (D)</p> Signup and view all the answers

What is the primary objective of using blood doping or erythropoietin in athletes?

<p>To enhance oxygen carrying capacity of blood to muscles (D)</p> Signup and view all the answers

Which of the following methods is considered legitimate for increasing one's blood oxygen levels?

<p>Training at altitude (D)</p> Signup and view all the answers

What is a significant consequence of blood doping in young athletes?

<p>Blood sludging and potential strokes (C)</p> Signup and view all the answers

Which performance-enhancing agent is commonly used by power athletes but has unclear effects on power activity?

<p>Growth hormone (C)</p> Signup and view all the answers

What is a notable medical application of erythropoietin?

<p>Address conditions of anemia with reduced aerobic capacity (C)</p> Signup and view all the answers

How much energy do fats and oils provide per gram?

<p>9 kcal (B)</p> Signup and view all the answers

What happens to triglycerides in adipose tissue during fasting?

<p>They are broken down, releasing fatty acids (A)</p> Signup and view all the answers

What percentage of the American diet is composed of energy derived from triglycerides and other lipids?

<p>35% (C)</p> Signup and view all the answers

What is the estimated risk of developing T2D if both parents have the condition and the individual becomes obese?

<p>90% (D)</p> Signup and view all the answers

Which of the following represents an important consideration in strength training regimens for optimal muscle gains?

<p>Using a progressively increasing 1-rep max (D)</p> Signup and view all the answers

What is the role of insulin in muscle anabolism?

<p>It has both direct and indirect effects on muscle growth. (C)</p> Signup and view all the answers

Which factor is believed to potentially increase muscle catabolism?

<p>Amino acid deficiency (B)</p> Signup and view all the answers

What type of exercise is most effective in increasing aerobic capacity?

<p>Endurance exercise training (B)</p> Signup and view all the answers

Which of the following hormones has a dose-response relationship that increases muscle anabolism?

<p>Testosterone (B)</p> Signup and view all the answers

How does high altitude training affect physical performance?

<p>Increases red blood cell production. (A)</p> Signup and view all the answers

What is one potential effect of glucocorticoids on muscle tissue?

<p>Causes protein breakdown. (C)</p> Signup and view all the answers

What is the primary effect of caffeine on exercise performance?

<p>Improves exercise time to exhaustion (D)</p> Signup and view all the answers

Which physiological parameter does VO2max primarily depend on in endurance athletes?

<p>Cardiac output (A)</p> Signup and view all the answers

What is the purpose of blood doping in athletic performance?

<p>To increase red blood cell count (D)</p> Signup and view all the answers

What is a major side effect associated with creatine supplementation?

<p>Weight gain (D)</p> Signup and view all the answers

What role does carbohydrates (CHO) play in relation to creatine?

<p>Enhances creatine uptake in muscles (C)</p> Signup and view all the answers

Which aspect of exercise performance does creatine supplementation improve?

<p>Strength and power (D)</p> Signup and view all the answers

What is the composition of creatine stored in muscle?

<p>1/3 as free creatine and 2/3 as phosphocreatine (B)</p> Signup and view all the answers

What is considered a performance-enhancing level of caffeine intake?

<p>Above 15 μg/ml (C)</p> Signup and view all the answers

Flashcards

Body Composition: Water

The body primarily consists of water, making up approximately 60-70% in children and about 50% in adults.

Cellular Protein Content

Cells, particularly lean tissue, are primarily composed of protein, roughly 20%.

Carbohydrate Stores

The body stores a minimal amount of carbohydrates, with the largest reserves found in the liver.

Thyroid Hormone and Energy Expenditure

The thyroid hormone regulates energy expenditure. A lower calorie intake leads to reduced activity of the thyroid hormone.

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Leptin Function

Leptin is a hormone secreted by fat cells, primarily responsible for informing the brain about energy stores.

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Calorie Restriction (CR)

The process of reducing caloric intake without causing malnutrition, typically 20-40% lower than normal consumption.

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Muscle Mass as a Nutritional Indicator

The measurement of muscle mass is crucial for assessing nutritional health, including brain development.

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D3-Creatine Dilution Method

A reliable method for measuring total body skeletal muscle mass using a single oral dose of D3-creatine.

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Functional Muscle Mass and Health

Functional muscle mass significantly impacts overall health and longevity.

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Calorie Restriction and Lifespan Extension

CR is a powerful intervention that has been shown to extend lifespan and healthspan in various organisms from worms to primates, including humans.

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Calorie Restriction and Age-Related Diseases

CR is a promising intervention for slowing down aging and preventing age-related diseases, such as cancer and neurodegeneration.

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Calorie Restriction for Human Health

CR is a potential strategy for enhancing human health and longevity.

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Stunted Growth and Interventions

Stunted growth is a significant public health issue, and interventions are being tested to address this problem.

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Fuel Selection Preference in Humans

When both carbohydrates (CHO) and fat are present in the body, CHO is preferentially used as fuel. This is due to the insulin response triggered by CHO, which inhibits fat oxidation and promotes CHO oxidation.

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Why Mice CR Might Not Apply to Humans

The study of calorie restriction (CR) in mice may not directly translate to humans due to differences in lifespan, cancer susceptibility, and metabolic rates.

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What is Calorie Restriction (CR)?

Calorie restriction (CR) involves a reduced caloric intake without malnutrition. It has been observed to extend lifespan in various species.

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Thyroid Axis and CR

The thyroid axis, which regulates metabolism, is affected by CR. T4/T3/TSH levels are altered, influencing energy expenditure.

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Hormonal Effects of CR on Growth and Reproduction

CR can impact growth and reproduction. Growth hormone (GH) and IGF-1 levels are reduced, leading to changes in gonadotropins and gonadal function.

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CR and Insulin Sensitivity

Calorie restriction can lead to an increase in insulin sensitivity. This means that the body becomes more responsive to insulin, which helps regulate blood sugar levels.

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Possible Mechanisms of CR

CR is thought to trigger various adaptations, including changes in cell turnover rates, stress resistance, and hormonal/metabolic signals. However, the exact mechanisms are unknown.

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CR and Cancer

CR might extend lifespan by reducing cancer risk, as it decreases cell division. Reducing cell division rates might be a key factor in longevity models.

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Heritability of T2D

A condition where family history strongly influences the likelihood of developing type 2 diabetes (T2D), even with obesity being a significant factor.

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Missing Heritability in T2D

The phenomenon where genetic research has identified only a small portion of the genes responsible for T2D, despite its strong hereditary nature.

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Strength/Resistance Training

A set of exercises that increase muscle size and strength, typically involving weightlifting or resistance bands.

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Muscle Anabolism

The process of building muscle tissue.

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Muscle Catabolism

The breakdown of muscle tissue.

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Aerobic Capacity

The ability of the body to utilize oxygen efficiently during prolonged physical activity.

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Increased Hematocrit

The process of increasing the number of red blood cells in the blood.

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Erythropoietin

A hormone that stimulates the production of red blood cells, often used to treat anemia.

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Blood Doping

Blood doping involves artificially increasing the red blood cell count, which boosts oxygen delivery to muscles. This can be achieved by storing and reintroducing a person's own blood, or by using erythropoietin.

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Autologous Blood Transfusion

Storing your own blood and re-injecting it before competition. This increases the volume of red blood cells, boosting performance.

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Anabolic Drugs

A class of drugs that stimulate muscle growth. These drugs are commonly used in medicine for treating various conditions.

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Growth Hormone

These drugs stimulate the production of growth hormone. Used medically for growth deficiencies and some other conditions.

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Creatine Supplements

Creatine is a substance naturally found in the body that is used for energy production. Supplements are marketed to boost muscle mass and strength, but their effectiveness remains debated.

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Fats

A type of fat that is solid at room temperature. It is a major form of lipid in food and the body.

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Fasting

The breakdown of stored fat when the body is lacking energy. This process releases fatty acids into the bloodstream.

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How does caffeine affect exercise performance?

Caffeine can increase time to exhaustion by 22-23% compared to placebo due to its effect on mobilizing free fatty acids and reducing reliance on glycogen as fuel.

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What is VO2max and what limits it?

The maximum amount of oxygen your body can use during exercise is your VO2max. It's limited by your heart's ability to pump blood (cardiac output) and the efficiency of your muscles in extracting oxygen.

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What is Blood Doping?

Blood doping involves taking out red blood cells before a competition and re-infusing them later to increase the red blood cell count. This leads to more oxygen being delivered to the muscles, enhancing performance.

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Explain the role of Creatine in exercise performance?

Creatine is a naturally occurring molecule that helps regenerate ATP, the energy currency in our muscles. It's found in muscle tissue and is taken up more readily with carbohydrates.

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What are the effects of creatine supplementation on exercise performance?

Creatine supplementation can lead to short-term improvements in strength, power, and sprint performance. Long-term use can contribute to greater gains in strength, sprint performance, and muscle mass.

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Why does creatine supplementation lead to weight gain?

When creatine enters muscle cells, it draws water along with it to maintain osmotic pressure, leading to a temporary increase in body weight. This is referred to as water weight gain.

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How can we get creatine in the diet vs. supplementation?

Creatine is naturally found in foods like meat, but supplements offer a more concentrated and controlled dose.

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Why does cooking affect creatine?

Cooking creatine destroys it and transforms it into creatinine, which is useless for muscle function. Therefore, it's important to consume raw creatine or use supplements.

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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.

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