Metabolism of Weight Loss 1

Question 1

Major organs of energy expenditure

Ratio of fuel sources

Compare 100 kcal of glycogen, protein and adipose tissue

Answer 1

Skeletal muscle, liver, brain (around 20%) then heart (9%), kidney (8%), adipose (4%)
LBM contributes the most to energy expenditure

Adipose TAGs weigh 2x protein but provide 4-5x the kcal. Glucose is minimally available in comparison

100 kcal glycogen or protein is 80% water in g, whereas 100 kcal of adipose is almost 100% energy

Question 2

Insulin independent tissues for glucose uptake

Insulin dependent tissues

Answer 2

Independent: Liver, CNS, RBC

Dependent: muscle, adipose (glucose also delivered by VLDL)

Question 3

Components of the blood glucose curve over 4 hours

Answer 3

Hour 1: insulin rises with glucose, increased absorption and glycolysis, decreased glycogenolysis and gluconeogenesis

Hour 2: insulin peaks, increased glucose uptake and glycogenesis

Hour 3: glucagon begins to rise (inverse job to insulin)

Steady phase: ratio of insulin to glucagon decreases while glycogenolysis and gluconeogenesis increases

Question 4

In response to a fed state there is an initial increase in __________ and initial decrease in ___________

Answer 4

Increase in: insulin, glucose, lactate, pyruvate, triglycerides, alanine, BCAA, total AA and I:G ↑

Decrease in: glucagon, FFAs, keto acids, glycerol and urea nitrogen

Question 5

Fed state response curve for glucose, lactate and pyruvate

Answer 5

Question 6

Fed state response curve for TAGs, FFA and ketone bodies

Answer 6

Question 7

Fed state response curve for glycerol, alanine and BCAAs

Answer 7

Question 8

Fed state response curve for total AA and urea nitrogen

Answer 8

Question 9

Normal vs insulin resistant blood glucose curves (photo)

Answer 9

In insulin resistance the glucagon response is not efficient which results in reactive hypoglycemia

Question 10

Rationale of the CHO-insulin model of obesity and summary of evidence

Answer 10

CHO raise insulin the most and therefore contribute most to weight gain - by eating a low glycemic diet can support weight loss
*Ratio of I:G dictates energy storage

But high CHO + high fat causes fat storage, not necessarily high GI foods specifically

Question 11

What is the energy paradox?

Answer 11

Brain requires 500 kcal of mostly glucose per day but most energy stored as fatty acids which cannot be converted to glucose

Question 12

Fuel Flux during Early Fasting vs Prolonged

Answer 12

Early fasting: BMR remains same
- Insulin ↓ in all tissues
- Normal protein breakdown
- Use of glucose as metabolic fuel for brain + RBCs
- glucagon ↑
- FA to liver and muscle

Prolonged fasting: BMR decreases
- ↓ protein breakdown
- glucagon levels out
- reduce glucose used as metabolic fuel including brain but RBC glucose stays stable
- ketone use by brain

Question 13

Over 48 hours how does glucose utilization + ketogenesis change during starvation?

Answer 13

Exogenous: Stage I, first 6 hours - rapid spike and decline

Glycogen: Stage II, small spike as exogenous bottoms out around 6 hours and then steady decline until 28 hours

Gluconeogenesis: Stage III Slow increase and then sudden fall in stage IV after 5-7 days, then gradual decrease

Ketogenesis: Steady linear increase from the end of exogenous glucose until it dominates in stage V after 1 week

Question 14

Tissues utilizing glucose in:

Answer 14

Stage 1: all

Stage 2: All except liver, muscle and AT diminished

Stage 3: All except liver, muscle and AT more diminished

Stage 4: Brain, RBC, renal medulla and some muscle

Stage 5: RBCs and renal medulla (brain at diminished rate)