Nancy Clark’sSports NutritionGuidebook:Carbohydrates
CHAPTER 6
FCS 342
Carbohydrate Review
Wholesome forms of carbohydrates are the best choices forfueling your muscles
◦Beneficial diet for people of all ages and athletic abilities:
◦Minimally processed carbohydrate-rich foods + adequate protein + healthyfat
…But how much is enough? How much is too much? Arecarbs good or bad?
◦Many myths and misconceptions surround carbohydrates
Carbohydrate Absorption
No matter which form of carbohydrate you intake, each willbe broken down into glucose
◦Glucose: Fuel for muscles and brain
Individuals absorb different forms of sugars at differentrates
◦No sugar is nutritionally superior to another
◦Consuming a variety of sugars during exercise allows for betterabsorption
◦Maltodextrins, commonly found in sports drinks, provide energy with rapidabsorption and less sweetness than table sugar
Carbohydrate Storage
Humans store extra glucose mostly in the form of muscleglycogen and liver glycogen
Sugars and starches (plant sugar) have similar abilities tofuel muscles, but different abilities to nourish muscles
◦Refined carbohydrates in sugary soft drinks
◦Provides kcals but no vitamins and minerals
◦Unrefined carbohydrates in fruits, vegetables, and whole grains
◦Provides kcals, vitamins, minerals, and fiber
Are Carbs Fattening?
Yes?
No?
The answer is: maybe.
◦Carbohydrates are not fattening by nature
◦Excess kcals are fattening
◦Particularly excess fat kcals
◦The conversion of excess carbs into body fat is limited because youburn carbs when exercising
Are Carbs Fattening?
BEWARE:
◦A continuous intake ofexcess kcals from carbswill eventually contributeto weight gain
◦When your glycogen storesare filled, the excess kcals arestored as body fat
Key Points
Carbohydrate-based foods are less fattening than fat-basedfoods
You need carbs to fuel muscles
You burn carbs during hard exercise
Excess kcals lead to weight gain
◦When dieting to lose weight, energize with wholesome carbs andlimit intake of fatty foods
◦For added satiety, pair minimally processed carbs in combinationwith proteins
Glycemic Index andAthletes
Endurance athletes: low-GI foods may help by providingsustained energy during long bouts of exercise
Immediately following exercise: high-GI foods may be bestto rapidly refuel the muscles
However, it’s easier to inform athletes to consume fruits,veggies, and whole grains that do not upset stomach anddiminish hunger
Carbohydrates & Exercise
To sustain energy:
◦Consume easily digested pre-exercise meal or snack
◦After the first hour of exercise, consume 200 – 350 kcals of carbs(~50 – 90 grams) per hour of endurance exercise
To rapidly refuel:
◦Consume 0.5 grams of carbs per 1 lb of body weight every two hoursfor 4 – 6 hours along with healthy fats and proteins
Carbohydrates & Exercise
Refuel example:
◦165 lb endurance athlete
◦How many grams of carbs would he need to consume every twohours for 4 – 6 hours?
◦Answer:
◦ ~83 grams every two hours for 4 – 6 hours
Carbohydrates forGlycogen
Glycogen = storage for of carbs
◦Carbs in muscles used during exercise
◦Carbs in liver released into bloodstream to maintain blood glucoselevels and provide energy to brain and muscles
When muscle glycogen stores become too low:
◦Hit the wall
◦Overwhelmingly fatigued
◦Yearn to quit
Carbohydrates forGlycogen
During low-level exercise:
◦Muscles burn primarily fats for energy
During light – moderate exercise:
◦Stored fat provides 50 – 60% of the fuel
During vigorous exercise:
◦Muscles depend on glycogen stores for energy
Carbohydrates forGlycogen
NOTE: well-trained muscles store ~20 – 50% more glycogenthan untrained muscles
◦Low-carb diets can potentially hurt performance
Research has found:
◦Low muscle glycogen stores at the start of exercise can jeopardizeperformance at the end of exercise
Conclusion:
◦Eat responsibly. Make carbs the main foundation of your meals.
Carbohydrates forGlycogen
Carbs are important for replacing depletedglycogen stores
Protein and fat are NOT stored as muscle glycogen
Carbohydrate Loading forEndurance Exercise: 9 Tips
1. Carbohydrate load daily:
◦2.5 – 3.0 grams carbs/lb body weight for ~1 hour/day moderateexercise
◦2.5 – 4.5 grams carbs/lb body weight for ~1 – 3 hours/day enduranceexercise
◦3.5 – 5.5 grams carbs/lb body weight for >4.5 hours/day extremeexercise
2. Taper your training:
◦Complete final endurance training 2 – 3 weeks before event
◦Reduce training load; still maintain some high-intensity workout bouts
Carbohydrate Loading forEndurance Exercise: 9 Tips
3. Eat enough protein: 0.5 – 0.8 grams per pound bodyweight to prevent muscle breakdown and enable repair
4. Do not fat load: 20 – 25% of total kcals
5. Pay attention to fiber intake to promote regular bowelmovements
6. Plan meal times carefully: oftentimes, it’s better to have alarge meal at breakfast or lunch the day before an event,rather than dinner
Carbohydrate Loading forEndurance Exercise: 9 Tips
7. Drink extra fluids to prevent dehydration (water or juice,not alcohol)
8. Be sensible about your selections
9. Eat breakfast on event day to prevent hunger andmaintain normal blood glucose
Depleted Liver Glycogen
When liver glycogen stores become depleted, athletes crash
◦Recall, when muscle glycogen stores become depleted, athletes “hit thewall”
Despite adequate muscle glycogen, an athlete may feel thefollowing symptoms due to inadequate sugar being released intothe bloodstream:
◦Uncoordinated
◦Light-headed
◦Unable to concentrate
◦Weakened
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