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Clinical Nutrition 1 > Metabolism of Weight Loss & Adaptations > Flashcards

Metabolism of Weight Loss & Adaptations Flashcards

1
Q

Which organs contribute the most to REE?

A

Liver (21%)

Brain (20%)

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2
Q

In 100 g of glycogen tissue how many grams of readily-available energy (glucose)?

A

20g

80 kcal

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3
Q

In 100 g of protein tissue, how many grams of energy (protien)?

A

20 g

80 kcal

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4
Q

To obtain 90 kcal from adipose tissue (fat), how much does the tissue weight?

A

10 g

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5
Q

Which tissues are GLUT4 dependant?

A

Heart, Muscle, Adipose

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6
Q

Which tissues are insulin independent?

A

Liver, CNS, RBC

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7
Q

On the blood glucose curve, what does the uptake slope depict (within 1 hour of ingesting a meal)?

A
  • Increased GI glucose absorption and insulin release
  • Decreased glycogenolysis, gluconeogeneisis
  • Increased glycolysis
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8
Q

On the blood glucose curve, what does the decay slope depict (1.5-3 hours after ingesting a meal)?

A
  • High insulin and high tissue uptake
  • Increase glycogenesis
  • Later, glucagon will increased
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9
Q

On the blood glucose curve, what does the steady phase depict (within 3-4 hours after ingesting a meal)?

A
  • Decrease I:G
  • Increased glycogenolysis
  • Increase gluconeogenesis
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10
Q

When will secretion of glucagon accur?

A

Approx 2.5 hours after meal

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11
Q

What causes most changes in substrate utilization and circulation?

A

Ratio of insulin to glucagon

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12
Q

An initial increase in I:G causes an increase in:
A) Triglycerides, Pyruvate, Alanine, Total Amino Acids
B) Lactate, Free Fatty Acids, Glycerol
C) Free Fatty Acids, Triglycerides, Insulin:Glucagon Ration

A

A)

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13
Q

An initial decrease in I:G causes an increase in:
A) Triglycerides, Pyruvate, Alanine, Total Amino Acids
B) Lactate, Free Fatty Acids, Glycerol
C) Free Fatty Acids, Triglycerides, Insulin:Glucagon Ration

A

B)

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14
Q

An initial increase in insulin causes an increase in:
A) Urea Nitrogen, Pyruvate, Alanine,
B) Lactate, Free Fatty Acids, Glycerol, BCAA
C) Free Fatty Acids, Glucagon, Urea Nitrogen Keto acid

A

C)

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15
Q

Free fatty acids originate from ?

A

LIPOLYSIS of adipose tissue in the FASTED state (decreased I:G ration)

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16
Q

Triglycerides in circulation originate from?

A

The meal during the FED state (from circulating VLDL, originating from fat or carbs) increased I:G ratio

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17
Q

Why does lactate increase during fed state?

A

Glucose available for RBCs to undergo anaerobic glycolysis

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18
Q

Why does pyruvate increase in the fed state?

A

I:G increases glycolysis

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19
Q

Why do TGs increase in circulation in the later, fed state?

A

After fat from diet or conversion from carbs is packed into VLDL, TGs will be given off into bloodstream and tissues

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20
Q

Why do FFAs decrease in the early fed sate?

A

Insulin inhibits lipolysis

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21
Q

Why do ketone bodies decrease after fed? Increase later?

A

Oxidation of glucose now sufficient to replenish TCA cycle, then, lower amounts of OAA inhibits anaplerosis of TCA cycle which drives ketone body synthesis.

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22
Q

Why does glycerol decrease in early fed state?

A

Insulin inhibits lipolysis

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23
Q

Why does alanine increase during fed state? Why does it decrease?

A

Flux of AA in diet. after feeding, alanine may be used for gluconeogenesis in the liver.

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24
Q

Why do BCAA increase during fed state and increase later in circulation?

A

Influx from diet, then increase later in circulation due to minor endogenous protein breakdown to maintain blood glucose homeostasis.

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25
Q

Why do total amino acids drastically increase after fed state?

A

Influx from diet PLUS insulin promote the active transport of amino acids into muscles and other tissues that must travel through bloodstream to support adequate protein synthesis.

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26
Q

Why does urea nitrogen decrease with an increase in total amino acids during fed state?

A

Amino acids are being used for protein synthesis and NOT endogenous protein breakdown, therefore urea production decreases.

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27
Q

What are the claims surrounding insulin in fad dieting?

A
  • Insulin is required to take up glucose into energy storage
  • The release of insulin is the “fed signal”
  • Carbohydrates have the most profound effect on insulin release, and are the most likely macronutrient to favour energy storage and weight gain
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28
Q

Why are carbohydrates often the target macronutrient in fat diets?

A

Since the have the most profound effect on insulin release, and are the most likely to favour energy storage and weight gain …

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29
Q

What would you counter with if someone claims that carbohydrates are the ultimate macronutrient that favours weight gain?

A

That possessing an energy balance within the excess of our needs ultimately determines if we will gain weight or not and does NOT depend on what kind of macronutrients that we are consuming

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30
Q

Why do diabetics experience reactive hypoglycemia? (brief period of hypoglycemia after fed state)

A

Their excessive secretion of insulin promotes a smaller secretion of glucagon.

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31
Q

What does reactive hypoglycemia cause?

A

Decrease in glycogenolysis and glucneogeneisis, less glucose available to estabish blood glucose homeostasis

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32
Q

What ratio dictates energy storage?

A

Insulin:Glucagon

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33
Q

Fed signal causes change in several _____ over a 4-hour period

A

blood parameters

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34
Q

Changes in ____ (2) are the basis for several fad diets?

A 
I:G
GI index (glucsoe cures)
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35
Q

What are the goals when adapting to fasting?

A
  • Meet energy needs
  • Meet glucose requirements
  • Spare protein (lean mass)
36
Q

Describe the energy paradox

A

Our brain needs 500 kcal of soluble fuels per day (usually glucose) but almost all energy is stored as FA and not glycogen. Fatty acids cannot be converted to glucose.

37
Q

Describe the fuel flux in early fasting (24 hours)

A
  • Insulin decrease and accelerates lipolysis
  • FFA fuel the heart
  • Blood glucose homeostasis supported by remaining glycogen, glycerol and gluconeogenic amino acids
  • Muscles participate in Cori/Cahill cycle
38
Q

What inhibits the suppression of lipolysis and proteolysis ?

A

Low insulin

39
Q

In prolonged fasting, we have established a __

A

decrease energy expenditure (1500 kcal)

40
Q

Describe the fuel flux is prolonged fasting

A
  • Glycogen stores exerted& less participation in gluconeogenesis by muscle inhibits anaplerosis of TCA cycle
  • Acetyl-Coa bulid-up and production of ketone bodies
  • Cori/Cahill cycles continue, but less contribution to glucose
41
Q

What are the main fuels in prolonged fasting?

A

Glucose (gluconeogenesis) and ketone bodies

42
Q

What are the main fuels in initial fasting?

A

Glycogen, free-fatty acids, gluconeogenesis

43
Q

What proportionally decreases as length of fasting increases?

A

proteolysis (inhibited by low I:G ration)

44
Q

What is used within the first hour of fasting?

A

Exogenous glucose

45
Q

After a 12 hour fast, what are the main fuels?

A

50/50 mix of glucose from glycogen and gluconeogenesis

46
Q

What increases linearly as fasting increases?

A

Ketogenesis

47
Q

What is the origin of blood glucose between 1-4 hours? What tissues use glucose?Main fuel for brain?

A

Exogenous
All
Glucose

48
Q

What is the origin of blood glucose between 4-16 hours? What tissues use glucose? Main fuel for brain?

A

Liver glycogen, gluconeogenesis
All except liver (Muscle and AT decrease)
Glucose

49
Q

What is the origin of blood glucose between 16-28 hours? What tissues use glucose? Main fuel for brain?

A

Liver gluconeogenesis, glycogen
All except liver (Muscle and AT decrease)
Glucose

50
Q

What is the origin of blood glucose between 2 and 24 days of fasting? What tissues use glucose? Main fuel for brain?

A
  • Gluconeogenesis from hepatic and renal
  • Brain, RBCs, renal medulla (small amount in muscle)
  • Glucose, ketone bodies
51
Q

What is the origin of blood glucose after 24 days of fasting? What tissues use glucose? Main fuel for brain?

A
  • Gluconeogenesis from hepatic and renal,
  • Brain decreased rate, RBCs, renal medulla
  • Ketone bodies, glucose
52
Q

Why does the brain use glucose at a decrease after 24 days of fasting vs RBCs and renal medulla?

A

RBCs and renal medulla absolutely dependant on glucose (derived from gluconeogenesis) whereas the brain can utilize ketone bodies for fuel

53
Q

Why is thee a high amount of NH4+ in urine after fasting?

A

As ketone body production exceeds renal capacities, will be spilled into urine where it must be buffered with NH4+, increasing urinary ammonia

54
Q

Endogenous protein breakdown occurs during fasting, how come this is not reflected by an increase in urea nitrogen AND ammonia?

A

If there is a high enough amount of ketone bodies being produced, this means that insulin is low we enough to suppress proteolysis, thus decreasing endogenous protein breakdown and consequently urea nitrogen.

55
Q

It is ideal that ketone bodies are buffered in the kidney with ammonia, but what tends to happen?

A

Usually buffered with K+, which could lea to hypokalemia

56
Q

(T/F) Even with normal renal function, there are serious health risks associate with ketoacids

A

F

57
Q

We should not advise the keto diet and should closely monitor patients at risk for starvation who have ____

A

decreased renal function, inability to salt out ketone bodies causing electrolyte an pH imbalance

58
Q

What is the most prominent ketone body in the well fed state? After 5wks starvation?

A

Acetoacetate

B-hydroxybutarate

59
Q

The key to energy deficit/decreased diets (weight-loss, starvation, surgery) is to increase _____ to establish ____ and prevent _____

A

protein
nitrogen balance
endogenous protein breakdown

60
Q

What puts a higher requirement on our protein needs in absence of sufficient energy intake?

A

Higher rate of proteolysis

61
Q

______, protein intakes should be higher to avoid endogenous protein breakdown

A

Dieting, weight loss, surgery, anorexia, starvation, low-carbohydrate diets

62
Q

An energy intake as high of ___ should establish a zero nitrogen balance in energy deficient diets

A

1.5 g/kcal/day

63
Q

What does the forbes equation describe?

A

Where the more body fat a person has, the less loss of lean body mass they will have during weight loss

64
Q

High body fat, ___ lean body mass during weight loss

A

LESS

65
Q

Low body fat, ___ lean body mass during weight loss

A

MORE

66
Q

In the forbes prediction (1) _____ will lose less nitrogen than thin people

A

Obese individuals (more fat, less endogenous protein breakdown)

67
Q

In the forbes prediction (2) the ____ the subject is, the less the contribution of LBM to total weight loss on energy restricted diets

A

fatter (more fat will contribute to weight loss, less LBM)

68
Q

Describe cardiovascular changes to severe and rapid weight loss

A
  • Decreased cardiac output, heart rate, BP and volume

- Tachardyia to compensate for decreased blood volume

69
Q

Describe renal changes to severe and rapid weight loss

A

Stress on kidney due to acid/base balance, ketones

70
Q

Describe immune function changes to severe and rapid weight loss

A

Impaired T-cell/lymphocyte function, less cytokines, overall smaller immune function

71
Q

Describe GI changes to severe and rapid weight loss

A
  • deceased lipid absorption (steatorrhea)

- decreases gastric, pancreatic and bile

72
Q

What explains the GI changes to severe and rapid weight loss?

A

Atrophy of villous surface area, less absorption especially of lipids

73
Q

Describe electrolyte changes to severe and rapid weight loss

A
  • Potassium losses

- Hypokalemia

74
Q

Could CNS be affected by severe and rapid weight gain?

A

Yes

75
Q

What causes refeeding syndrome?

A

As we shift back from ketone bodies to glucose, there is a major influx of insulin and and huge uptake of glucose into the starved cells

76
Q

During refeeding syndrome, what causes a lot of intracellular molecules to follow into the cell with glucose?

A

Recall Na+/Glucose pump, if lots of glucose in, lots of sodium out causing molecules to travel from hight to low into the cell

77
Q

What is the HALLMARK of refeeding syndrome?

A

Movement of PHOSPHORUS into the intracellular space

78
Q

What electrolyte imbalances are characteristic of refeeding syndrome?

A

Hypophosphatemia
Hypokalemia
Magnesium

79
Q

What electrolyte imbalances are characteristic of refeeding syndrome?

A

Hypophosphatemia
Hypokalemia
Hypomagnesemia

80
Q

What are the 6 main physiological changes during repletion (EGB-INS)

A
  • ECF expansion
  • Glycogen synthesis
  • Increased BEE
  • Increased insulin
  • sodium retention
  • Cell synthesis, growth and rehydration
81
Q

Why should sodium and fluid intake be limited?

A

Introduction of CHO into diet after starvation (insulin) and inhibits renal excretion of sodium and water - may cause cardiac arrythmias

82
Q

What are the steps in refeeding? (FMPS)

A
  • Normalize fluid and electrolyte imbalances
  • Provide mixed diet to JUST match energy expenditure
  • Provide protein at 1,.5-2g/kg/day at CURRENT body weight
  • Monitor serum electrolytes, weight, intake and output
83
Q

What is indicative of refeeding syndrome?

A

Very rapid weight gain, which is likely water which means that fluid andelectrolyte imbalances are occuring

84
Q

What is indicative of refeeding syndrome?

A

Very rapid weight gain, which is likely water which means that fluid and electrolyte imbalances are occurring

85
Q

How much glucose should we give a patient at risk for refeeding syndrome?

A

100-150 g of glucose to stop LBM. Start with 25% of dose and increase gradually while monitoring electrolytes

86
Q

In addition to K+, phosphate and Mg, what else may be supplemented and why?

A

Thiamine - needed in glucose metabolism

87
Q

On first day of refeeding, what should protein intake be?

A

20g/day to allow for urea cycle enzymes to adapt

Clinical Nutrition 1 (30 decks)

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