Carbohydrate and Fat Utilization During Exercise

1. Carbohydrate and Fat Utilization During Exercise Presented and Prepared by: Lauren Reppucci Maria Ramirez Professor Steven Dion

2. Key Terms • ØCARBOHYDRATES THEY CONTAIN CARBON AND WATER, AND ARE THE PERFERED FUEL SOURCE DURING INTENSE EXERCISE. • ØATP SUPPLIES THE ENEGY FOR ALL FORMS OF BIOLOGIC WORK. • ØTCA CYCLE FATS AND CARBOHYDRATES ARE BURNED IN THE MITOCHONDRIA.

3. Terms Continued • ØFAT 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. • ØCLYCOGEN 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.

4. Terms Continued • ØGLYCOGEN PHOSPHORYLASE AUGMENTS GLYCOGEN BREAKDOWN IN THE LIVER AND ACTIVE MUSCLE. • ØGLUCOSE CAN ALSO BE CALLED DEXTROSE, OR BLOOD SUGAR, OCCURS NATURALLY IN FOOD. THE DIGESTION OF COMPLEX CARBOHYDRATES CAN PRODUCE GLUCOSE. • ØTRIGLYCERIDES 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.

5. Energy Substrate Comes in Two Varieties • Carbohydrates • Fats • In Two Sources • Intramuscular • Blood

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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 The Benefits of Exercise At Any Intensity

16. 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 To Sum It All Up

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