Fuel homeostasis

Metabolic Rate

total rate of body energy use (measured by heat or O2 consumption)

What does BMR stand for?

Basal Metabolic Rate

Basal Metabolic Rate

the minimum amount of energy needed by the body to remain alive

How is BMR measured?

In a conscious individual who is relaxed and has not eaten in the previous 12-14 hour period, standardized for STP, diet, and body size.

Lipogenesis

fat synthesis

Lipolysis

fat breakdown

Gluconeogenesis

new formation of glucose

Glycolysis

glucose breakdown

Glycogenolysis

breakdown of glycogen into glucose

What are the two states in regard to metabolism?

absorptive and post-absorptive

Absorptive state

occurs during and for about 4 hours after eating (all during GI absorption of food)

Body’s main energy source

absorbed glucose

3 uses of CHO

burned for energy, production of glycogen (liver and skeletal muscle), production of fat (liver and adipose)

This state is dominated by ______

Insulin

Insulin

stimulated to secretion by: increased glucose in plasma, increase in plasma AA, GI hormones, parasympathetic NS, inhibited by decreased plasma glucose and sympathetic stimulation

Effects

CHO:

• increase glucose uptake in all cells (but brain and liver)

• stimulates glycolysis

• increase glycogen synthesis/decrease glycogenolysis

• inhibits gluconeogenesis in liver

Net effect

increase glucose uptake and use → decrease plasma glucose

Lipid

increase lipogenesis and decrease lipolysis; increase FA uptake

Net effect

decrease FA and glycerol in plasma: increase fat storage

Post absorptive state (fasting state)

occurs after absorption of meal finished; body must switch to reserves for energy

Dominated by

glucagon

Glucagon

stimulated by decreased glucose in plasma, increased AA in plasma, sympathetic activity, and epinephrine; inhibited by increase glucose and parasympathetic activity

Actions:

Lipolysis (adipose tissue) (glucose sparing action) - increase FA in plasma for energy use (leaves glu for CNS)

the liver can convert FA into ketone bodies which can be used by cells (and brain in a prolonged fast) as energy

Glycogenolysis (liver)

releases glu to blood

Gluconeogenesis (liver(

conversion of lactate, pyruvate and glycerol to glucose;and AA to glucose (source of protein is skeletal muscle and others)

Net actions:

increase glu, FA, glycerol, and ketones