GLYCAEMIC INDEX IN SPORT NUTRITION:
METABOLIC RESPONSES AND PHYSICAL
PERFORMANCE
Sareena Hanim Hamzah, PhD
BSc (Mal), MMedSci, PhD (Glasgow)
Deputy Director of Research & Development
Sports Centre
University of Malaya
Kuala Lumpur, MALAYSIA
ANSSH 2015, TAIPEI, TAIWAN.
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Presentation Overview
• Glycaemic Index and postprandial responses
• Glycaemic Index in Sport Nutrition
- Metabolic responses pre-, during and postexercise /recovery
• GI and fuel storage
• GI and performance in different type of exercise
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Glycaemic Index and postprandial responses
• Glycemic index
(GI) is a ranking
of CHO foods
based on their
immediate
effect on blood
glucose levels
(Jenkins et al. 1981)
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Glucose and insulin responses
Similar responses were observed in plasma insulin
concentration
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Suppression of lipolysis under condition of
increased insulin concentration
Adipocyte
TAG
(+ Insulin) – inhibit HSL
(-) Lipolysis
(+)
Esterification
Glycerol 3-P
Glycerol
FFA
ATP
Blood glucose
CoA
Fatty acyl CoA
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(-)Blood
Glycerol
(-)Blood
FFA
- Reduced the
uptake of fatty
acids by muscle
cells and thus
diminished fat
oxidation
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Glycaemic Index in Sport Nutrition
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Glycaemic Index in Sport Nutrition
What does the research say?
Pre-exercise
Pre-exercise meal (2g CHO/kg) with LGI consumed 2-3 hours prior
exercise resulted
- higher rate of fat oxidation
- lower CHO utilisation
- promote sustained CHO availability during exercise
(Febbraio et. al., 2000; Wu et. al., 2003; Wee et. al., 2005)
- better performance (Wu & William et. al., 2006)
than HGI.
These studies are in agreement with a recent study carried out on GI
pre-exercise meal when consume 90 min prior to exercise. (Sun et. al.,
2013)
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Glycaemic Index in Sport Nutrition
GI CHO feeding before exercise
1. HGI
• Higher blood glucose levels
• Higher insulin levels
• Higher suppression of
plasma free fatty acids
• Lower rate of fat oxidation
• Higher rate of CHO
oxidation
• Higher glycogenolysis
Wu et al 2003, Wu & Williams 2006
Wee et al 2005
Stevenson et al 2005
Mondazzi & Arcelli 2009
Sun et al. 2013
2. LGI
• Lower blood glucose levels
• Lower insulin levels
• Lower suppression of
plasma free fatty acids
• Higher rate of fat oxidation
• Lower rate of CHO oxidation
• Glycogen sparing &
extended availability of
glucose sources
Greater endurance capacity
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Glycaemic Index in Sport Nutrition
however….
• 10 male cyclist consumed
HGI or LGI meals (1g
CHO/kg) 45 min before
performing 40 km TT
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Findings
• Higher CHO oxidation in LGI
• Lower fat oxidation in LGI
• No difference in FFA levels
between HGI & LGI
LGI meal increase availability of CHO
and greater CHO oxidation
throughout exercise and improved
TT
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Glycaemic Index in Sport Nutrition
40 km TT
- Greater CHO
availability
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Glycaemic Index in Sport Nutrition
What does the research say?
During exercise
Effect of pre-exercise glycemic-index meal on running when
CHO-electrolyte solution is consumed during exercise.
Wong et. al., 2009. Int J Sport Nutr Exerc Metab. 19(3):222-42
• 9 men run at 70% VO2max for 21
km on a treadmill after
consuming HGI or LGI CHO (1.5
g/kg) meal 2 h prior or after
overnight fast
• During trial, 2 ml/kg of a 6.6%
CHO-electrolyte solution
immediately before exercise and
every 2.5 km after the start of
running.
Findings :-There were no
differences in total CHO and fat
oxidation throughout the trials.
When a CHO-electrolyte solution
is consumed during a 21-km run,
the GI of the pre-exercise CHO
meal makes no difference in
running performance.
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Glycaemic Index in Sport Nutrition
What does the research say?
Post-exercise and recovery
• High CHO with HGI diet consumed over a recovery period of
24 hours resulted a greater increase in muscle glycogen
storage than in the isocaloric LGI diet. (Burke et. al., 1993)
• The greater accumulation of muscle glycogen following the
HGI diet was a result of the greater insulinemic response
favouring muscle glycogen resynthesis (Burke et al., 1993;
Stevenson et. al., 2005)
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Glycaemic Index in Sport Nutrition
Post-exercise and recovery
• When GI foods were consumed during 24 h recovery
between bouts of prolonged strenuous exercise, fat
oxidation rates and FFA concentrations were higher
following the LGI during subsequent exercise than in
the HGI diet and therefore increased endurance
capacity. (Stevenson et. al., 2005).
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Glycaemic Index and Fuel Storage
Effect of high and low glycaemic index recovery diets on
intramuscular lipid oxidation during aerobic exercise.
Trenell et. al., 2008. British Journal of Nutrition, 99, 326-332.
7 endurance-trained, cycled 90 min
at 70 % VO2peak, consumed either
HGI or LGI meals (8 g CHO/kg) over
the following 12 h.
Findings
The following day after an
overnight fast, the 90 min cycle was
repeated.
-Reduce FFA availability was
reduced in the HGI trial
IMTG content of the vastus lateralis
was quantified using magnetic
resonance spectroscopy before and
after exercise.
->2-fold greater reduction in IMTG
in the HGI trial than the LGI trial
HGI reduces FFA availability during
exercise and increase reliance on
IMTG as a substrate source during
moderate intensity exercise
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Glycaemic Index and Fuel Storage
• HGI increase glycogen synthesis – glycogen storage
- insulin-independent (short recovery)
• mediated by GLUT4
• low glycogen concentration, glycogen synthase
- insulin-dependant
- depending on timing of intake
• LGI increase IMTG storage
- high CHO recovery diet reduces the post-exercise
resynthesis of IMTG (Decombaz et al., 2001)
- LGI diet may favour IMTG resynthesis over a HGI
diet but results have been inconsistent.
* Substrate utilization influenced by pre-exercise muscle
substrate level.
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GI and high intensity intermittent exercise
• 10 males 4 females
• Back-to-back 90 min
intermittent high intensity
treadmill running
separated by 3 h
• HGI & LGI consumed 2 h
before and within 1 hr after
Results
A LGI improved the
metabolic profile before
and during extended high
intensity intermittent
exercise.
Did not effect performance
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GI and high intensity intermittent exercise
Effects of GI meals on intermittent exercise.
Hulton et. al., 2012. Int J Sports Med; 33(9):756-62
• 9 male recreational football players
• Performed a football specific protocol followed by 1 km TT
• HGI & LGI meals was consumed 3.5 h prior
Results
• No significant impact on performance or metabolic responses
during 90 min of intermittent high intensity exercise
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Conclusions
1. LGI pre-exercise meal enhances fat utilization during endurance
exercise than HGI but may not translate into performance
2. HGI meal consumed during recovery promotes higher glycogen
synthesis and storage compared to LGI. Higher glycogen storage
increases glycogenolysis.
3. LGI meal consumed during recovery between bouts of prolonged
exercise increases free fatty acid and rate of fat oxidation during
subsequent exercise than HGI
4. LGI increases IMTG storage, HGI reduces FFA availability and
increases IMTG utilization.
5. GI of CHO pre-exercise meals may not benefit high intensity
intermittent exercise.
6. GI of CHO consumed during exercise?
SHOULD GI TO BE CONSIDERED IN SPORT NUTRITION?
I WELCOME FOR ANY SUGGESTION AND OPINION
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References
Burke, L. M., Collier, G. R., & Hargreaves, M. (1993). Muscle Glycogen-Storage After Prolonged Exercise - Effect of the Glycaemic
Index of Carbohydrate Feedings. Journal of Applied Physiology, 75, 1019-1023.
Decombaz, J., Schmitt, B., Ith, M., Decarli, B. H., Diem, P., Kreis, R., Hoppeler, H., & Boesch, C. (2001). Post-exercise fat intake
repletes intramyocellular lipids but no faster in trained than in sedentary subjects. American Journal of Physiology-Regulatory
Integrative and Comparative Physiology, 281, R760-R769.
Jenkins, D. J. A., Wolever, T. M. S., Taylor, R. H., Barker, H., Fielden, H., Baldwin, J. M., Bowling, A. C., Newman, H. C., Jenkins, A.
L., & Goff, D. V. (1981). Glycaemic Index of Foods - A Physiological-Basis for Carbohydrate Exchange. American Journal of Clinical
Nutrition, 34, 362-366.
Stevenson, E., Williams, C., McComb, G., & Oram, C. (2005b). Improved recovery from prolonged exercise following the
consumption of low glycaemic index carbohydrate meals. International Journal of Sport Nutrition and Exercise Metabolism, 15,
333-349.
Trenell, M. I., Stevenson, E., Stockmann, K., & Brand-Miller, J. (2008). Effect of high and low glycaemic index recovery diets on
intramuscular lipid oxidation during aerobic exercise. British Journal of Nutrition, 99, 326-332.
Wee, S. L., Williams, C., Tsintzas, K., & Boobis, L. (2005). Ingestion of a high-glycaemic index meal increases muscle glycogen
storage at rest but augments its utilization during subsequent exercise. Journal of Applied Physiology, 99, 707-714.
Wu, C. L. & Williams, C. (2006). A low glycaemic index meal before exercise improves endurance running capacity in men.
International Journal of Sport Nutrition and Exercise Metabolism, 16, 510-527.
Wu, C. L., Nicholas, C., Williams, C., Took, A., & Hardy, L. (2003). The influence of high-carbohydrate meals with different
glycaemic indices on substrate utilisation during subsequent exercise. British Journal of Nutrition, 90, 1049-1056.
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