Carbohydrate and Fat
Utilization During Exercise
Presented and Prepared by:
Lauren Reppucci
Maria Ramirez
Professor Steven Dion
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Key Terms

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
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
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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
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 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
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Carbohydrates
Fats
In Two Sources
Intramuscular
Blood
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Exercise Intensity and Duration
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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
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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
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Carbohydrates come in two sources
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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
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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 - Intensity
low-medium-high-very high
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Low intensity

Walking – energy output can be generated entirely
by peripheral fat stores releasing free fatty acids
The 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
fat release and uptake does not stop –
it plateaus and another source is provided to
makeup the needed generation rate
 Peripheral
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Medium Intensity
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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
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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
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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
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Low intensity exercise is
not the 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
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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
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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
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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
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THE END
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