NUSCTX 10 MIDTERM 3 EXAM QUESTIONS
WITH COMPLETE ANSWERS 2026
⩥ basics of body composition. Answer: - body is mostly made of water
(around 60-70% in children and adults)
- cells aka lean tissue are composed of about 20% protein, this is true for
all cells. ex: ~ 30 kg muscle x 20% = 6 kg protein x 4 Kcal/kg = 24,000
Kcal
- maximum carb stores in the body are miniscule. ex: liver: ~5% x 1.5
kg = 75 g x 4 Kcal/g = 300 Kcal. muscle: <1% x 30 kg = 300 g x 4
Kcal/g = 1200 Kcal
- most body energy stores are in triglycerides in adipose tissue (there is
also structural fat and membrane lipids in cells)
- total energy content of fat in body: ~20% x 70kg = ~15 kg x ~9 Kcal/g
= ~ 135,000 Kcal
⩥ fuel composition of normal humans. Answer:
⩥ lean tissue conservation achieved in starvation. Answer: - normal
protein losses = intake = 100g protein/day
- because people are generally in nitrogen balance, losses of nitrogen
from body must equal intake
- if you fasted for 30 days at this rate = 3 Kg protein lost, and every 100g
protein = ~ 500 g lean tissue (1 lb of muscle lost a day) so 15 Kg of lean
tissue lost
,- we have no purely "storage proteins" in the body, all proteins in lean
tissue have function
⩥ lethal LBM loss. Answer: loss of 40-50% LBM, therefore a loss of
~15 kg LBM can be life-threatening. we should be able to starve < 30
days, by these calculations
⩥ how long can we starve and stay alive?. Answer: - hunger strikes in
prison, people stranded without food, etc: newspapers show up after 30-
45 days
- survival can be 60-90 days or more, if hydration and electrolytes are
maintained
⩥ how is starvation and staying alive possible?. Answer: - by reducing
nitrogen losses to 20g protein/day (3g N) = 100g lean tissue lost/day
instead of 500 g/day --> we can survive starvation much longer
⩥ sequential metabolic response to prolonged fasting. Answer: - phase
1: glycogen depletion; high rate of nitrogen loss; baseline fuel mixture is
maintained (first few days)
- phase 2: fatty acid oxidation; ketosis; reduced nitrogen and tissue-
losses (~ 7 days)
- phase 3: brain keto-adapation; greatly reduced nitrogen and tissue
losses; further adaptations (kidney, endocrine, behavioral) --> 3 g
Nitrogen lost/ a day
,- key to this is the brain: stops using only glucose, thereby reducing need
for gluconeogenesis from amino acids
⩥ liver's role in orchestrated metabolic response to starvation. Answer:
glycogen depletion; reduced glucose release into blood; lowers blood
glucose, insulin levels; increased fatty acid oxidation/ketosis; reduced
gluconeogenesis fro amino acids to supply the grain
⩥ pancreas's role in orchestrated metabolic response to starvation.
Answer: reduced insulin secretion
⩥ adipose's role in orchestrated metabolic response to starvation.
Answer: increased fatty acid release into blood
⩥ muscle's role in orchestrated metabolic response to starvation.
Answer: reduced glucose oxidation; increased fat oxidation; reduced
protein breakdown & amino acid release
⩥ brain's role in orchestrated metabolic response to starvation. Answer:
keto-adaptation (can use ketones); reduced glucose oxidation;
dramatically reduced amino acid use from proteins for gluconeogenesis
⩥ kidney's role in orchestrated metabolic response to starvation. Answer:
conservation of ketones
, ⩥ endocrine organs's role in orchestrated metabolic response to
starvation. Answer: multiple adaptations
⩥ why do we lose nitrogen at all?. Answer: - comparison to beans
germinating
- comparison to bears hibernating
⩥ why is nitrogen lost at all during starvation?. Answer: some glucose
for brain and inefficiencies of the core metabolism? nobody really
knows why, but we are built this way
⩥ hormonal consequences of starvation or semi-starvation in growth.
Answer: consequences for height of populations
⩥ hormonal consequences of starvation or semi-starvation in
reproductive system. Answer: (gonadotropins, gonadal function): health
implications in modern world (timing of menarche; aerobic, athletes,
anorexia nervosa; breast cancer)
⩥ hormonal consequences of starvation or semi-starvation in thyroid
axis (T4,T3,TSH). Answer: utility and downside in obesity
⩥ hormonal consequences of starvation or semi-starvation in insulin
sensitivity. Answer: therapeutic uses
WITH COMPLETE ANSWERS 2026
⩥ basics of body composition. Answer: - body is mostly made of water
(around 60-70% in children and adults)
- cells aka lean tissue are composed of about 20% protein, this is true for
all cells. ex: ~ 30 kg muscle x 20% = 6 kg protein x 4 Kcal/kg = 24,000
Kcal
- maximum carb stores in the body are miniscule. ex: liver: ~5% x 1.5
kg = 75 g x 4 Kcal/g = 300 Kcal. muscle: <1% x 30 kg = 300 g x 4
Kcal/g = 1200 Kcal
- most body energy stores are in triglycerides in adipose tissue (there is
also structural fat and membrane lipids in cells)
- total energy content of fat in body: ~20% x 70kg = ~15 kg x ~9 Kcal/g
= ~ 135,000 Kcal
⩥ fuel composition of normal humans. Answer:
⩥ lean tissue conservation achieved in starvation. Answer: - normal
protein losses = intake = 100g protein/day
- because people are generally in nitrogen balance, losses of nitrogen
from body must equal intake
- if you fasted for 30 days at this rate = 3 Kg protein lost, and every 100g
protein = ~ 500 g lean tissue (1 lb of muscle lost a day) so 15 Kg of lean
tissue lost
,- we have no purely "storage proteins" in the body, all proteins in lean
tissue have function
⩥ lethal LBM loss. Answer: loss of 40-50% LBM, therefore a loss of
~15 kg LBM can be life-threatening. we should be able to starve < 30
days, by these calculations
⩥ how long can we starve and stay alive?. Answer: - hunger strikes in
prison, people stranded without food, etc: newspapers show up after 30-
45 days
- survival can be 60-90 days or more, if hydration and electrolytes are
maintained
⩥ how is starvation and staying alive possible?. Answer: - by reducing
nitrogen losses to 20g protein/day (3g N) = 100g lean tissue lost/day
instead of 500 g/day --> we can survive starvation much longer
⩥ sequential metabolic response to prolonged fasting. Answer: - phase
1: glycogen depletion; high rate of nitrogen loss; baseline fuel mixture is
maintained (first few days)
- phase 2: fatty acid oxidation; ketosis; reduced nitrogen and tissue-
losses (~ 7 days)
- phase 3: brain keto-adapation; greatly reduced nitrogen and tissue
losses; further adaptations (kidney, endocrine, behavioral) --> 3 g
Nitrogen lost/ a day
,- key to this is the brain: stops using only glucose, thereby reducing need
for gluconeogenesis from amino acids
⩥ liver's role in orchestrated metabolic response to starvation. Answer:
glycogen depletion; reduced glucose release into blood; lowers blood
glucose, insulin levels; increased fatty acid oxidation/ketosis; reduced
gluconeogenesis fro amino acids to supply the grain
⩥ pancreas's role in orchestrated metabolic response to starvation.
Answer: reduced insulin secretion
⩥ adipose's role in orchestrated metabolic response to starvation.
Answer: increased fatty acid release into blood
⩥ muscle's role in orchestrated metabolic response to starvation.
Answer: reduced glucose oxidation; increased fat oxidation; reduced
protein breakdown & amino acid release
⩥ brain's role in orchestrated metabolic response to starvation. Answer:
keto-adaptation (can use ketones); reduced glucose oxidation;
dramatically reduced amino acid use from proteins for gluconeogenesis
⩥ kidney's role in orchestrated metabolic response to starvation. Answer:
conservation of ketones
, ⩥ endocrine organs's role in orchestrated metabolic response to
starvation. Answer: multiple adaptations
⩥ why do we lose nitrogen at all?. Answer: - comparison to beans
germinating
- comparison to bears hibernating
⩥ why is nitrogen lost at all during starvation?. Answer: some glucose
for brain and inefficiencies of the core metabolism? nobody really
knows why, but we are built this way
⩥ hormonal consequences of starvation or semi-starvation in growth.
Answer: consequences for height of populations
⩥ hormonal consequences of starvation or semi-starvation in
reproductive system. Answer: (gonadotropins, gonadal function): health
implications in modern world (timing of menarche; aerobic, athletes,
anorexia nervosa; breast cancer)
⩥ hormonal consequences of starvation or semi-starvation in thyroid
axis (T4,T3,TSH). Answer: utility and downside in obesity
⩥ hormonal consequences of starvation or semi-starvation in insulin
sensitivity. Answer: therapeutic uses
