Nancy Clark’s Sports Nutrition Guidebook: Carbohydrates CHAPTER 6 FCS 342

Carbohydrate Review Wholesome forms of carbohydrates are the best choices for fueling your muscles ◦Beneficial diet for people of all ages and athletic abilities: ◦Minimally processed carbohydrate-rich foods + adequate protein + healthy fat …But how much is enough? How much is too much? Are carbs good or bad? ◦Many myths and misconceptions surround carbohydrates

Carbohydrate Absorption No matter which form of carbohydrate you intake, each will be broken down into glucose ◦Glucose: Fuel for muscles and brain Individuals absorb different forms of sugars at different rates ◦No sugar is nutritionally superior to another ◦Consuming a variety of sugars during exercise allows for better absorption ◦Maltodextrins, commonly found in sports drinks, provide energy with rapid absorption and less sweetness than table sugar

Carbohydrate Storage Humans store extra glucose mostly in the form of muscle glycogen and liver glycogen Sugars and starches (plant sugar) have similar abilities to fuel 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 you burn carbs when exercising

Are Carbs Fattening? BEWARE: ◦A continuous intake of excess kcals from carbs will eventually contribute to weight gain ◦When your glycogen stores are filled, the excess kcals are stored as body fat

Key Points Carbohydrate-based foods are less fattening than fat-based foods 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 and limit intake of fatty foods ◦For added satiety, pair minimally processed carbs in combination with proteins

Glycemic Index and Athletes Endurance athletes: low-GI foods may help by providing sustained energy during long bouts of exercise Immediately following exercise: high-GI foods may be best to rapidly refuel the muscles However, it’s easier to inform athletes to consume fruits, veggies, and whole grains that do not upset stomach and diminish 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 hours for 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 two hours for 4 – 6 hours? ◦Answer: ◦ ~83 grams every two hours for 4 – 6 hours

Carbohydrates for Glycogen Glycogen = storage for of carbs ◦Carbs in muscles  used during exercise ◦Carbs in liver  released into bloodstream to maintain blood glucose levels and provide energy to brain and muscles When muscle glycogen stores become too low: ◦Hit the wall ◦Overwhelmingly fatigued ◦Yearn to quit

Carbohydrates for Glycogen 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 for Glycogen NOTE: well-trained muscles store ~20 – 50% more glycogen than untrained muscles ◦Low-carb diets can potentially hurt performance Research has found: ◦Low muscle glycogen stores at the start of exercise can jeopardize performance at the end of exercise Conclusion: ◦Eat responsibly. Make carbs the main foundation of your meals.

Carbohydrates for Glycogen Carbs are important for replacing depleted glycogen stores Protein and fat are NOT stored as muscle glycogen

Carbohydrate Loading for Endurance Exercise: 9 Tips 1. Carbohydrate load daily: ◦2.5 – 3.0 grams carbs/lb body weight for ~1 hour/day moderate exercise ◦2.5 – 4.5 grams carbs/lb body weight for ~1 – 3 hours/day endurance exercise ◦3.5 – 5.5 grams carbs/lb body weight for >4.5 hours/day extreme exercise 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 for Endurance Exercise: 9 Tips 3. Eat enough protein: 0.5 – 0.8 grams per pound body weight 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 bowel movements 6. Plan meal times carefully: oftentimes, it’s better to have a large meal at breakfast or lunch the day before an event, rather than dinner

Carbohydrate Loading for Endurance 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 and maintain normal blood glucose

Depleted Liver Glycogen When liver glycogen stores become depleted, athletes crash ◦Recall, when muscle glycogen stores become depleted, athletes “hit the wall” Despite adequate muscle glycogen, an athlete may feel the following symptoms due to inadequate sugar being released into the bloodstream: ◦Uncoordinated ◦Light-headed ◦Unable to concentrate ◦Weakened

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