2. Dietary Carbohydrates
• One of the most important nutrients in your diet,
from the standpoint of both health and athletic
performance, is dietary carbohydrate.
3. What are the different types of dietary
carbohydrate?
• Carbohydrates
– Carbon, hydrogen and oxygen
• Simple carbohydrates
– Monosaccharides
• Name them
– Disaccharides
• Name them and the monosaccharides for each
4. What are some common foods high in
carbohydrate content?
5. How much carbohydrate do we need in
the diet?
• Recommended Dietary Allowance (RDA)
– 130 grams
• Acceptable Macronutrient Distribution Range
(AMDR)
– 45-65% of energy intake
• Daily Value (DV)
– 60% of daily energy needs
– 300 grams on a 2,000 Calorie diet
– 25 grams of fiber
6. Recommended carbohydrate in the diet
• Sport nutritionists
– Recommend high end of AMDR
– 60-70% or higher
– Diet containing 3,000 Calories
• 450 grams of carbohydrate at 60% level
8. What happens to the carbohydrate after it
is absorbed into the body?
• Most dietary carbohydrates eventually are converted
to glucose which circulates in the blood
• Carbohydrate foods have different effects on blood
glucose levels
• The glycemic index and glycemic load
9. Fates of blood glucose
• May be used for energy
• May be converted to liver or muscle glycogen
• May be converted to and stored as fat in adipose
tissues
• May be excreted in the urine if in excess
12. Carbohydrates for Exercise
• Carbohydrate as an energy source during exercise
• Effect of training on carbohydrate metabolism
• Methods of providing carbohydrate
– Before competition
– During competition
– After competition
– During training
13. In what type of activities does the body rely
heavily on carbohydrate as an energy source?
• Carbohydrate contributes about 40% of energy
needs at rest
• Fat is main energy source during low exercise
intensity, such as 40-50% VO2max
• Carbohydrate is major source during
– Very high intensity anaerobic exercise
– High intensity (>65% VO2max) aerobic exercise
– Prolonged aerobic exercise events
– Intermittent high-intensity exercise sports
14. Carbohydrate sources for exercise
• Muscle glycogen is a very important source
• Liver glycogen is converted to blood glucose
• Blood glucose is delivered to muscles
15. Hypoglycemia
• The human body attempts to prevent hypoglycemia
• Hormone activity
– Insulin
– Glucagon
16. Hormones and glucose metabolism
Hormone Gland Stimulus Action
Insulin Pancreas Increase in blood
glucose
Helps transport
glucose into cells;
decreases blood
glucose levels
Glucagon Pancreas Decrease in blood
glucose; exercise
stress
Promotes
gluconeogenesis in
liver; helps increase
blood glucose levels
Epinephrine Adrenal Exercise stress;
decrease in blood
glucose
Promotes glycogen
breakdown and
glucose release
from the liver
Cortisol Adrenal Exercise stress;
decrease in blood
glucose
Promotes
breakdown of
protein; stimulates
gluconeogenesis
17. How is low muscle glycogen related to the
development of fatigue?
• Low muscle glycogen and aerobic exercise
– Muscle glycogen is the primary fuel for endurance
athletes, such as marathon runner
• Studies have shown physical exhaustion to be
associated with very low muscle glycogen levels.
However, other studies have shown fatigue with
some muscle glycogen remaining.
19. When, how much, and in what form should
carbohydrates be consumed before or during exercise?
• Athletes who may benefit from carbohydrate intake
– Endurance exercise
– Intermediate high-intensity exercise
• Fluid replacement is also an important consideration
20. What is the importance of carbohydrate
replenishment after prolonged exercise?
• Rapid restoration of muscle glycogen important for
some athletes
– Repeated bouts of prolonged, intense exercise on the
same day
– Prolonged, intense exercise on consecutive days
21. Carbohydrate-rich diets for athletes
• Sport nutritionists recommend that athletes
consume about 8-10 grams of carbohydrate per
kilogram body weight daily
• For a 70-kg athlete, this would amount to 560 to 700
grams of carbohydrate daily, or the equivalent of
2,240 to 2,800 Calories
• On a 3,500-Calorie daily intake, the carbohydrate
would provide 65-80% of daily energy intake.
• This amount of daily carbohydrate would help
restore muscle glycogen levels
22. Carbohydrates during training
• There is no evidence that low-carbohydrate diets
improve exercise performance
• A diet rich in healthy carbohydrates may help
guarantee optimal energy sources for daily training
• Train high and compete high is the concept of
training and competing with high carbohydrate
intake.
23. Carbohydrate loading
What is carbohydrate, or glycogen, loading?
• Method of increasing muscle glycogen levels
– Also known as muscle glycogen supercompensation
24. What type of athlete would benefit from
carbohydrate loading?
• Athletes who sustain high levels of continuous
energy expenditure for prolonged periods
– Long-distance runners
– Cross-country skiers
– Endurance triathletes
– Tournament play in intermittent high-intensity exercise
sports
25. How do you carbohydrate load?
• Athlete should be fully trained
• Classic procedure not necessary:
– Depletion stage
– Low carbohydrate diet
– Carbohydrate loading
• Have about 3-4 days of high carbohydrate intake, about 8-10 grams/kg
body weight, or more
• Low and high glycemic index carbohydrates are equally effective
• Taper exercise training over the course of a week or longer
27. Will carbohydrate loading increase muscle
glycogen concentration?
• Most studies report increased muscle glycogen levels
following carbohydrate loading procedures
• Both males and females will increase glycogen levels
if adequate energy and carbohydrate are consumed
• Muscle glycogen levels may increase two to three
times above normal
• Experiment with the protocol during training
28. Will carbohydrate loading improve
exercise performance?
• In general, the procedure is not needed for exercise
tasks of short duration
• In general, research supports the use of
carbohydrate loading as a means to enhance
performance in prolonged endurance exercise tasks
– Helps maintain an optimal pace longer
– Extra body water may help during exercise in the heat
• Most appropriate protocol is to use both
carbohydrate loading and consumption of
carbohydrate during the event
30. Soluble and insoluble fiber
• The issue of soluble and insoluble fiber
– Difficult to generalize on different health effects
of soluble and insoluble fiber; health effects are
due to total fiber, but it may be illustrative to
discuss soluble and insoluble fiber effects on
health.