Class 13- integrated metabolism, pt 2Feasting and Fasting

During times of feasting, metabolism tends to favour xxx

formation.

This can be done using all macronutrients; however, the

most direct and efficient process occurs from xxx

During times of feasting, metabolism tends to favour fat

formation.

This can be done using all macronutrients; however, the

most direct and efficient process occurs from dietary fat.

During feasting, how is fat broken down and stored?

Note: MOST favoured, direct and efficient.

• During digestion TG are broken down into 2 fatty acids and 1 monoglyceride ( 1 FA + glycerol). Absorbed, then put back together

During feasting, how are carbs broken down and stored?

CHOs must be:

1.digested/split to glucose,

absorbed,

2.dismantled to pyruvate,

3. converted to acetyl CoA,

4.then many CoA’s assembled into FA chains, then 3 FAs + 1 glycerol

= 1 TG.

During feasting, how is protein broken down and stored?

if there is excess protein

A) body tends to respond with enhanced protein oxidation (breakdown) for energy or repair purposes .

THEN

B) If still more additional excess, then protein becomes deaminated and the carbon skeleton used to convert to

FAs (or ketone bodies), can be transformed into TG and stored as Fat

When there is an excess of all macronutrients,

what does the body do first?

1. Carbohydrate ingested first replaces glycogen stores or is

oxidized and used for energy (brain, RBC, nerves)

2. Additional excess Carb converted to fat,

3. Excess fat ingested goes to fat.

Body “deals” with the excess Carb as the “easiest and

quickest” energy source to use, and then any ingested fat is

promoted toward storage

What happens during fasting? Body first breaks down xxx then yyy, where are they stored? Once broken down what are they used for?

What is Hormone-sensitive lipase?

• responsible for releasing free fatty acids (FFAS) from adipose tissue into circulation as a significant energy source for most tissues by catalyzing the hydrolysis of wide-ranging substrates like triacylglycerol, diacylglycerol, monoacylglycerol, cholesteryl ...

• responds to hormones such as epinephrine and

  glucagon which indicate a need for Fuel

What is Gluconeogenesis

Body synthesizing glucose from NON-CARBOHYDRATE carbons

What happens when Fasting Beyond

Glycogen Depletion?

How does the body adapt during starvation.?

What are ketone bodies, when are they produced and where

-3 types =acetoacetate, beta-hydroxybutyrate, and

acetone

• Water soluble

• produced by the liver from fatty acids

• produced during periods of low food intake (fasting),

carbohydrate restrictive diets, starvation,

prolonged intense exercise, alcoholism, or in

untreated (or inadequately treated) type 1

diabetes mellitus.

How does the formation of ketone bodies differ from FA oxidation? What happens during ketosis

Normally in FA oxidation: Acetyl CoA’s go through TCA cycle and the breakdown proceeds all the way to CO2and H20.

VS in ketosis, an intermediate is formed when the CoA’s are removed.

• Acidic

• Too much in blood lowers pH

• Fruity odour on breath (acetone)

• Ketosis causes loss of appetite. Loss

of appetite an advantage during

starvation

What are the 3 diff carb levels in a low carb diet

• strict keto diet=would typically have 20 to 50

grams of carb.

• “very low” carb diet = 51 to 100 grams

carb

• “low carb” diet= 100 to 130 grams carb

What are side effects from low carb diet

• Nausea

• Fatigue (especially if physically active)

• Constipation

• Low blood pressure

• Elevated uric acid (which may exacerbate kidney disease and cause inflammation of the joints in those predisposed to gout)

• Stale, foul taste in the mouth (bad breath)

• In pregnant women, fetal harm and stillbirth

What happens during prolonged glucose deprivation ? How does the body conserve energy

• brain and nerve cells develop the ability to derive

ONLY about 2/3s of their minimum energy

requirements from ketone bodies. Ketone

bodies can not sustain life by themselves!!

• Starvation or fasting for too long will cause

death, even if the person still has body fat,

because some protein is being used and

eventually major organs will be affected by

protein loss.

• Hormones slow metabolism

• Reduced energy output

• With water, can live up to 2 months or more

depending on some individual factors (such as fat

stores and muscle stores) prior to the starvation