34 Questions
During short-term fasting (overnight - ~24hrs), which hormone dominates in maintaining blood glucose levels?
Insulin
In early starvation (first ~7 days), what sustains serum glucose levels when glycogen is depleted?
Serum FFAs and Ketones
In long-term starvation (> 1 week), what sustains serum glucose levels at 4mM?
Proteins
What happens to urea synthesis in early starvation?
It decreases
Why does urinary NH4 rise sharply in early starvation?
To conserve nitrogen
What is the major energy source in early starvation (first ~7 days)?
Serum FFAs and Ketones
What sustains blood glucose levels at 5.1mM when glycogen stores are depleted?
Liver glucose
What is the preferred energy source for the brain during starvation?
Glucose
What hormone dominates during short-term fasting to maintain blood glucose levels when glycogen stores are depleted?
Insulin
What happens to glycogen stores during overnight fasting (~12-14hrs)?
They are depleted almost immediately
What is the most common compensatory behavior associated with bulimia?
Laxative abuse
Which of the following is a feature associated with binge eating disorder (BED)?
High blood pressure and cholesterol
What percentage of female adolescents are dissatisfied with their body?
50-80%
What is a common comorbidity in eating disorders?
Anxiety disorders
What is the estimated recovery rate for anorexia nervosa (AN) if diagnosed in early adolescence?
70-75% full recovery
What is the surface area of the gastrointestinal (GI) tract approximately?
270 m2
What is the intestinal microbiota primarily composed of?
Bacteria, archaea, and eukarya
What is the main difference between the intestinal microbiota and microbiome?
Microbiota refers to the community of microorganisms, while microbiome refers to their genetic material
What is the outcome for bulimia nervosa (BN) if treated within the first 5 years?
80% recovery
What is a common feature associated with Avoidant/Restrictive Food Intake Disorder (ARFID)?
Picky eating since childhood
What is the fate of urea synthesized in the urea cycle?
Excreted into the urine by the kidneys
During long-term starvation, what becomes the major energy source for the body?
Free fatty acids and ketones
What is the main role of skeletal muscle in the context of metabolic pathways?
Supplies amino acids for gluconeogenesis and ketogenesis
What is a characteristic feature of anorexia nervosa?
Intense fear of gaining weight
What are the associated emotional changes in bulimia nervosa?
Mood swings and anxiety
What is the main impact of eating disorders on physical health?
Osteoporosis and electrolyte imbalances
What is the primary source of fuel for certain tissues, produced from fatty acid oxidation in liver mitochondria?
Ketone bodies
What are the physical symptoms associated with anorexia nervosa?
Decreased sleep, dizziness, and weakness
What was the aim of the Minnesota Starvation Experiment in 1945?
To gain insight into the physical and psychological effects of semi-starvation
What percentage of female adolescents are dissatisfied with their body?
80%
What is the estimated recovery rate for anorexia nervosa (AN) if diagnosed in early adolescence?
70-75%
What is the surface area of the gastrointestinal (GI) tract approximately?
300 m2
What is the main difference between the intestinal microbiota and microbiome?
Genetic material
What is the main impact of eating disorders on physical health?
Electrolyte imbalance
Study Notes
Metabolic Pathways and Eating Disorders
- Ketone bodies are a special source of fuel and energy for certain tissues, produced from fatty acid oxidation in liver mitochondria.
- Urea is composed of two -NH2 groups joined by a carbonyl and is synthesized in the urea cycle, with two nitrogen atoms entering as NH4+ and aspartate.
- Urea diffuses from the liver to the blood and is excreted into the urine by the kidneys, with part of it diffusing from the blood to the intestine and being excreted in feces.
- During long-term starvation (> 1 week), there is a steady rise in free fatty acids (FFAs) and ketones, which become the major energy source, leading to adaptation and reduced nitrogen losses.
- Skeletal muscle supplies the liver with amino acids (AAs) for gluconeogenesis and ketogenesis, while adipose tissue releases FFAs for energy and liver repackaging.
- The liver undergoes ketogenesis from skeletal muscle AAs and adipose FFAs, converts adipose FFAs into very-low-density lipoproteins (VLDLs), and disposes of nitrogen as urea in the short term and NH4 in the long term.
- The body adapts to burn ketones and FFAs, sparing glucose for the brain and red blood cells, with metabolic responses including a decrease in resting metabolic rate and physical performance impairment.
- The Minnesota Starvation Experiment in 1945 involved 36 conscientious objectors and aimed to gain insight into the physical and psychological effects of semi-starvation, with participants experiencing anemia, fatigue, apathy, extreme weakness, and other issues.
- Eating disorders such as anorexia nervosa, bulimia nervosa, and binge-eating disorder have distinct diagnostic criteria and associated features, with anorexia nervosa characterized by low body weight, intense fear of gaining weight, and distorted body image.
- Anorexia nervosa is associated with low mood, anxiety, mood swings, social withdrawal, reduced sexual interest, impaired concentration, and physical changes like decreased sleep, dizziness, headaches, and weakness.
- Bulimia nervosa is characterized by recurrent binge-eating, followed by compensatory behaviors, and is associated with emotional changes, cognitive impairment, and physical symptoms such as decreased body temperature, heart rate, and metabolism.
- Eating disorders have serious implications for physical and mental health and can lead to severe physical complications like osteoporosis, electrolyte imbalances, and growth retardation.
Test your knowledge of metabolic pathways and their relationship to eating disorders with this quiz. Explore the synthesis of ketone bodies, urea, and the adaptation to long-term starvation, while also learning about the physical and psychological effects of eating disorders such as anorexia nervosa and bulimia nervosa.
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