carbohydrate and fat utilization during exercise 24 july 16

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Carbohydrate and Fat Utilization During Exercise

Developed by: AQ Khan

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Key Terms CARBOHYDRATES they contain carbon

and water, and are the perfered fuel source during intense exercise.

ATP supplies the enegy for all forms of biologic work.

TCA CYCLE fats and carbohydrates are burned in the mitochondria.

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Terms Continued FAT a molecule that has the same structural

elements as a carbohydrate except that it differs in its linkage of atoms. fats are commonly known as lipids.

CLYCOGEN stored in active muscle supplies almost all of the energy in the translation from rest to moderate, submaximal exercise, just as it does in intense exercise.

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Terms Continued GLYCOGEN PHOSPHORYLASE augments

glycogen breakdown in the liver and active muscle.

GLUCOSE can also be called dextrose, or blood sugar, occurs naturally in food. the digestion of complex carbohydrates can produce glucose.

TRIGLYCERIDES the simple lipids, or neutral fats. they are the most plentiful fats of the body. they constitute the major storage form of fat in the adipose (fat) cells.

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Energy Substrate Comes in Two Varieties

Carbohydrates Fats

In Two SourcesIntramuscularBlood

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Exercise Intensity and Duration For all energy substrates, carbs and fats,

ultimately ATP is generated in the muscle cell as the high energy substrate for moving muscle.

Energy can be generated aerobically or anaerobically

Fats and carbs get burned in mitochondria by the TCA cycle

Carbs can also be broken down in the absence of oxygen for limited energy production

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FAT SOURCES Fat for fuel is in the form of free fatty acids

Two sources of these fats are Peripheral fat stores

• Rolls of fat on the belly Intramuscular fat

• Triglyceride stored in the actual muscle

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CARBOHYDRATE SOURCES Carbohydrates come in two sources

Simple sugar glucose Storage form of glucose –glycogen

Glycogen is stored in • Muscles• Liver• Blood (smallest percent in blood)

The liver is the only tissue that can release stored glycogen in the form of glucose

A function of the liver is to maintain blood sugar levels by releasing glucose through gluconeogenesis and glycogenolysis

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Fuel Utilization is Determined by Energy Output or Intensity Level

Primarily first thing in the morning before you eat breakfast your energy demands are very low and can be met mainly by fat derived from blood free fatty acids

Free fatty acids are released at a low rate by peripheral fat stores

This allows the muscles to preserve both intramuscular fat and glycogen stores

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Fuel Utilization - Intensitylow-medium-high-very high

Low intensity Walking – energy output can be generated entirely

by peripheral fat stores releasing free fatty acidsThe removal rate of free fatty acids by muscle cells is faster than at rest and after 20-30 minutes, there will be a stimulus to increase free fatty acid release to maintain sufficient blood concentrations of free fatty acids for efficient removal by the working muscles

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Medium Intensity At medium intensity levels, you exceed the

capacity of peripheral fat stores to supply enough free fatty acids to meet energy output rates Intramuscular triglyceride is broken down to

provide more fat Peripheral fat release and uptake does not stop –

it plateaus and another source is provided to makeup the needed generation rate

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Medium Intensity A medium intensity pace can be maintained until either your

instramuscular fat stores are depleted or you run out of glycogen When the glycogen is depleted then protein is degraded

for three reasons Amino acids can be burned for energy much like carbs Some amino acids (branched chain ones) can supply

TCA cycle intermediates to maintain aerobic energy production derived from fat burning

Some amino acids (like alanine) are secreted into the bloodstream, picked up by the liver and converted into glucose

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High Intensity High Intensity exercise goes

above the limits of energy production rates that fats can supply and requires additional energy derived from sugar

The reason for this is that sugar requires less oxygen per unit of energy

At lower intensities, the energy production rate is low enough that oxygen is plentiful enough for fat burning

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Very High Intensity At very high intensities the aerobic system

reaches its limitations for energy generation (fat or sugar)

The anaerobic system takes over Only a little of the potential energy of glucose

is released but it is done so in a very rapid manner to meet short duration and very high energy production rates

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The Benefits of Exercise At Any Intensity

Low intensity exercise is not the best form for weight loss

Intramuscular stores (fat or glycogen) are depleted During the recovery

phase (post exercise) fats and carbs from the diet will go to restoring those levels

High intensity exercise can lead to fat loss because with depletion of glycogen those glycogen stores must be replenished with dietary carbs that would otherwise be burned for energy

While that storage process is occurring, the body will burn extra fat to supply current energy needs

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To Sum It All Up High intensity exercise

has its limitations because that pace cannot be maintained for a long period of time

Total calories burned will be limited

Consuming some form of glucose during the exercise to maintain energy may be necessary for performance consideration only

It is unnecessary to consume any form of glucose during an exercise workout with a duration of two hours at a moderate intensity if weight loss is your goal

Aerobic exercise improves the body’s ability to burn fats for energy Therefore no additional

supply of fuel is needed at the time

Liver Glycogen

BloodGlucose

MuscleGlycogen

Carbohydrate Stores after an Overnight FastSedentary

4 grams100

grams

400grams

Liver Glycogen

BloodGlucose

MuscleGlycogen

Carbohydrate Stores after an Overnight Fast 1 hr of Exercise

4 grams100

grams

400grams

Liver Glycogen

BloodGlucose

MuscleGlycogen


4 grams100

grams

400grams

Liver Glycogen

BloodGlucose

MuscleGlycogen


4 grams100

grams

400grams

!!!

The Most Efficient Fuel depends on Exercise Intensity and DurationMetabolic Efficiency

CHO is preferred during high intensity exercise because its metabolism yields more energy per liter of O2 than fat metabolism.

kcal/l of O2

CHO 5.05 Fat 4.74

CHO can also produce energy without O2!!!

Storage EfficiencyFat is preferred during prolonged exercise because its metabolism provides more energy per unit mass than CHO metabolism.

kcal/g of fuel

CHO 4.10 Fat 9.45

Fats are stored in the absence of H2O.

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THE END

carbohydrate and fat utilization during exercise 24 july 16

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