Carbohydrate and Fat Utilization During Exercise

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Carbohydrate and Fat Utilization During Exercise

• Presented and Prepared by
• Lauren Reppucci
• Maria Ramirez
• Professor Steven Dion

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Key Terms

• Ø      CARBOHYDRATES THEY CONTAIN CARBON AND
  WATER, AND ARE THE PERFERED FUEL SOURCE DURING
  INTENSE EXERCISE.
• Ø      ATP SUPPLIES THE ENEGY FOR ALL FORMS OF
  BIOLOGIC WORK.
• Ø      TCA CYCLE FATS AND CARBOHYDRATES ARE
  BURNED IN THE MITOCHONDRIA.

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Terms Continued

• Ø      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.
• Ø      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

• Ø      GLYCOGEN PHOSPHORYLASE AUGMENTS
  GLYCOGEN BREAKDOWN IN THE LIVER AND ACTIVE
  MUSCLE.
• Ø      GLUCOSE CAN ALSO BE CALLED DEXTROSE, OR
  BLOOD SUGAR, OCCURS NATURALLY IN FOOD. THE
  DIGESTION OF COMPLEX CARBOHYDRATES CAN PRODUCE
  GLUCOSE.
• Ø     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 Sources
• Intramuscular
• Blood

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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
  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
• 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 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 bodys ability to
  burn fats for energy
• Therefore no additional supply of fuel is needed
  at the time

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THE END