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Fats as ergogens

This article explores the role of fat as a fuel source during exercise and its impact on health. It discusses the different types of lipids, dietary recommendations, and fat metabolism during exercise. The study also examines the effects of fat loading and fat adaptation on glycogen utilization and performance in endurance athletes.

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Fats as ergogens

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  1. Fats as ergogens

  2. Fat bad, Carbohydrate good • Traditionally fat as an ingested fuel source during exercise has been considered taboo • Conversely, the ability to oxidize fat preferentially during exercise has been the holy grail • Carbs thought of as the preferred macronutrient ingested prior to or during exercise

  3. Generally, high dietary fat intake is associated with high incidence of heart disease and other maladies • Fat also has more energy per unit mass (9 cal/gram) • Contributes to caloric surplus and fat gain

  4. Why is fat oxidation over glycogen the holy grail • Typical energy stores in the form of glycogen for a well fed athlete • 2500 cal • Typical energy stores in the form of triglycerides for a well fed athlete • >100,000 cal

  5. Fat good • Fats essential for many biological processes • Membrane phospholipids • Steroids • Transport of lipid soluble vitamins

  6. Types of Lipids • Triglycerides • Glycerol and fatty acid • Storage form of fat in humans • Free fatty acid • Ingested fats released into blood • Triglycerides broken down and released into blood • Phospholipids • Structural • Steroids • Regulatory

  7. Types of fatty acids • Saturated • Bad fats • Monounsaturated • Olive oil • Polyunsaturated (PUFA) • Essential fatty acids • Must be ingested in diet • Omega 3 and omega 6, linoleic acid, alpha linoleic acid, arachidonic acid

  8. http://www.kumc.edu/research/medicine/biochemistry/bioc800/lip01fra.htmhttp://www.kumc.edu/research/medicine/biochemistry/bioc800/lip01fra.htm

  9. Dietary recommendations • < 30% of the diet should come from fat in sedentary individuals • Athletes may need greater caloric intake, but fat intake should not increase in absolute terms • ~20-25 % calories from fat • Many athletes may restrict fat intake to below 15% • Impairs regulatory functions, vitamin transport, membrane integrity

  10. Types of fat in the diet • Although sedentary or active individuals may consume less than 30% of calories from fat, high proportion typically from saturated fats • Keep saturated fat intake less than 10% of caloric intake • PUFAs should constitute 20% (equal amounts of omega 3 and omega 6) • Tough to do without supplements

  11. Fat/lipid metabolism during exercise

  12. The Substrate Utilization Paradox • As exercise intensity increases, the relative contribution from fat oxidation decreases • During light to moderate exercise though, the increase in oxygen consumption offsets the relative decrease in contribution from fat • Up to ~60 – 70 % • No lactate accumulation

  13. Muscle fuel sources in highly trained endurance athletes

  14. Also, as duration of exercise progresses, relative contribution from fat metabolism increases • Decrease in RER after several hours of light intensity exercise • Determined by substrate availability and oxidative capacity

  15. Contributions of four energy sources over prolonged time in endurance athletes

  16. Fat loading • Vukovich et al (1993) • Randall cycle • Glucose fatty acid cycle?? • At rest active in heart, diaphragm and skeletal muscle

  17. Prior studies • In support • In rats elevated FFA and heparin decreased carbohydrate utilization and spared glycogen • Confirmed in humans • Against • TG (MCT and LG) feeding to rats did not spare glycogen • Hargreaves saw no effect in one-legged knee extensions (intralipid)

  18. Purpose • Compare saturated (Costill) vs unsaturated (hargreaves) to see if differential effect • Exercise for 60 min at 70 % VO2max

  19. Results?

  20. What did they decide? • Fat loading decreased glycogen utilization in both intralipid and fat feeding trials • Greater elevation in FFA levels with FF did not result in greater glycogen sparing compared to intralipid

  21. Fat adaptation • Burke et al (2001) • Fat adaptation may be advantageous over fat loading for prolonged exercise

  22. Prior studies • Same lab reported 5-day adaptation to high fat/low carb diet resulted in increased fat oxidation and reduced glycogen oxidation during 2 hr cycling at 70 % VO2peak • 2 fold increase in fat oxidation vs control • No clear advantage during 30 min TT following 2 hr bout

  23. Blood glucose availability during the TT may play a role in performance • If maintain or elevate blood glucose during bout, does increased fat oxidation persist? • If so, does this result in improved performance?

  24. Purpose • Determine if enhanced fat oxidation with 5 day high fat diet persist with high CHO availability • Ho: High CHO intake would eliminate increased fat oxidation

  25. Results

  26. What did they decide? • 5-day adaptation to high fat diet enhanced fat oxidation during exercise despite increased CHO availability • CHO/glycogen sparing still enhanced to levels observed in low CHO availability • These adaptations still did not enhance performance in the TT at the end of the 2 hr bout

  27. Fat adaptation and ultraendurance • Carey et al (2001) • More on the fat adaptation diet and increased CHO availability

  28. Prior studies • Same lab showed previously that 5-day adaptation to high fat diet and increased CHO availability before and during 2 hr bout, increased fat oxidation and decreased CHO oxidation, but did not improve performance in subsequent 30 min TT

  29. Maybe the bout was not sufficient intensity or duration to deplete glycogen stores • If this is the case, increased fat oxidation may not be of benefit until glycogen is depleted

  30. Purpose • Determine if fat adaptation and increased CHO availability spare CHO during 4 hr cycling bout > 65% VO2peak and improves performance in subsequent 1 h TT

  31. Results

  32. What did they decide? • Fat adaptation did result in significant sparing of CHO during the 4 hr bout • Performance in subsequent TT was not enhanced (p=0.11)

  33. http://www.kumc.edu/research/medicine/biochemistry/bioc800/lip01fra.htmhttp://www.kumc.edu/research/medicine/biochemistry/bioc800/lip01fra.htm

  34. Intramuscular TG Utilization • Intramuscular triglyceride oxidation is dependent upon exercise intensity and duration • In animals, whole body exercise to exhaustion results in decreases in intramuscular TG content • Lower intensity exercise, results are equivocal

  35. Intramuscular TG utilization is also fiber type dependent • FOG>SO>FG

  36. In humans using various modes of exercise, TG content of VL decreased 25-50 % • Exercise prolonged at 55-70 % VO2max • During intense exercise 5 min in duration, TG decreased 29 % • Significant contribution of oxidative metabolism at 5 min

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