Dietary Recommendation for Athletes

Dr. David L. Gee FCSN/PE 446

Training Diet Recommendations: High Carbohydrate Diet

 For “Power Athletes”  Traditional recommendation – > 55% of calories  Why?

– primary source of energy – effect of repeated high intensity workouts on glycogen

Training Diet Recommendations: High Carbohydrate Diet

 For “Endurance Athletes”  Traditional recommendation – > 60% of calories  Why?

– endurance training reduces glycogen – repeated training effects

ADA/ACSM Position Paper Dietary Carbohydrates

    6-10 gCHO/kg BW – – Upper end with high intensity Upper end with long duration Recommends against % CHO guidelines 4000 Cal/day @ 50%CHO for 70kg athlete – = 7.1 gCHO/kg 2000 Cal/day @ 60%CHO for 60kg athlete – = 5 gCHO/kg

Training Diet Recommendations: High Carbohydrate Diet

 Recovery Meal  CHO ingested within 2hrs of workout is converted to glycogen 50% more rapidly.

– Rec: up to 1.5 g CHO/kgBW of mixed CHO within 2 hours (hi glycemic index?) – Particularly important for multiple workouts/events per day  Role for protein in recovery meal?

Training Diet Recommendations: High Carbohydrate Diet: Recovery Meal

   Example: – – 50 kg x 1.5 gCHO/kg = 75gCHO = 5 servings of bread or fruit Whole/real foods preferred – Cheapest, has other nutrients Sport Supplements – – – Convenient Concentrated Expensive

High CHO Energy Drinks

Energy Bars > 70% carbohydrate calories

Sport Shakes

Energy Gels

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Training Diet Recommendations: Moderate Protein Diet

RDA = 0.8 gP/kgBW 

For “Power Athletes”

    ACSM/ADA: – 1.6-1.7gP/kgBW maintenance of large muscle mass optimizes rate of protein synthesis (?) Is more protein a problem?

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Training Diet Recommendations: Moderate Protein Diet

For “Endurance Athletes” ACSM/ADA: – 1.2-1.4gP/kgBW replaces proteins used as fuel during endurance training (10-15% of energy)

Training Diet Recommendations: Moderate Protein Diet

 Most athletes do

NOT

consume supplementary amounts of protein need to    typical US diet: 15% of calories 4000 Cal diet = 150g Pro in the diet 90 kg “Power athlete” needing 1.6gP/kg = needs 144g Pro

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Which athletes are at risk for inadequate protein intake?

Limited caloric intake – – – low meat/dairy intake very low fat intake weight conscious athlete 2000 Calorie, 10% protein = 200 PRO Cal = 50g PRO provided 1.6 gPRO x 55 kg = 88g PRO needed

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5 c NF milk, $2/gal, 40gP, $0.63

Training Diet Recommendations:Low Fat Diet

 >55-60% CHO, 10-15% PRO 

< 25% FAT

 Advantages of moderately low fat (compared to very low fat) – High caloric density – – Wider variety of foods available May be more palatable

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Training Diet Recommendations: Summary

Carbohydrates – Moderate to high in carbohydrates » 6-10g CHO/kg BW Protein – Higher than RDA, moderately high – Power athletes: 1.6-1.7gP/kgBW – Endurance athletes: 1.2-1.4gP/kgBW Fat – Balance of calories, relatively low fat – <25% of calories

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Case Study: Brian Competitive Stair Runner

Works 7AM to 3:30PM – Construction contractor in Boston suburbs Training Schedule – 5X/week for 2 hours on stairs » 3 hour RT commute to city – Trains weekends by cycling/trail runs Diet – Realizes he needs hi CHO diet – Eats convenience foods

Brian’s Diet and Training Schedule

       6:30AM: lg bowl cereal, banana, whole milk 7AM: coffee w/cream&sugar, doughnut 12noon: spaghetti with butter, 1-2 slices bread w/butter, 4 Oreo cookies, 2c whole milk 4-5:30PM: drives to Boston 5:30-7:30PM: trains 7:30-9PM: 16 oz sport drink while driving home 10PM: mac & cheese (frozen dinner), handful of crackers, 2 c milk, 4 Oreos, or a fast-food burger, fries, 2c milk

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Brian’s Diet Analysis

4000 Cal, 50% CHO, 15% PRO, 35% Fat Assume 160 lbs = 73kg PRO needs = 1.4gPRO/kg x 73 = 102gPRO – PRO intake = 4000 x 15% = 600 Cal PRO » = 150 g PRO, protein intake is OK » Or 150g/73kg = 2.1 gP/kgBW CHO intake = 4000 x 50% = 2000 Cal CHO » = 500 g CHO » = 6.8 g CHO/kg » CHO intake OK, but perhaps marginal Goal: – Increase CHO, decrease FAT intake – Recognize need for convenience

Case Study: Weight Gain for a Professional Basketball Player

 25 yo CBA rookie  7’1” (2.2m)  215 lbs (98kg) – BMI = 20 – Goal weight 235 lbs

24 hour diet recall

PRO: 97g/98kg=1.0gP/kg CHO: 1011g/98=10.3g/kg

Diet analysis of 24-hr recall

Revised food list

PRO: 174g/98kg = 1.8gP/kg CHO: 782g/98kg = 8.0gP/kg

Revised diet analysis

Pre-Event Meal

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Goals

 “Top off” glycogen stores  Optimize hydration 

Empty upper GI tract

Pre-Event Meal

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Meal Composition

 High in carbohydrates – mixed complex and simple  Reasonably low in fats and protein  Low in dietary fiber

Pre-Event Meal

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Composition (cont.)

 High in fluids  Individualize – Use familiar foods

Pre-Event Meal

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Timing of meal

– Complete > 2 hours before event  Individualize

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Carbohydrates Just Prior to Event

Purpose: provide exogeneous CHO to avoid hypoglycemia and delay glycogen depletion.

   For endurance athletes only – Absorption delayed Response highly individualized Caution: – May promote reactive hypoglycemia in sensitive individuals

Meals/CHO before/during/after events

    Pre-event/Pre-game meal – 2-3 hours before event CHO immediately prior to event – 5-15 minutes before event CHO during event Post-workout meal – Within 2 hours of workout

Carbohydrates During Event

   Sport drinks, energy bars, fruits, breads Metabolically useful for –

endurance athletes

» May spare muscle/liver glycogen » May provide extra CHO for more power –

those prone to hypoglycemia

» Exogenous source of glucose for blood Dilute concentration (<10%) may be advantageous because it also promotes fluid absorption

Types of Carbohydrate

 Fructose – Absorbed more slowly than glucose » Reduced insulin response – » » Reduced chance of reactive hypoglycemia  May produce more stable blood sugar if consumed 45 minutes prior to exercise May cause osmotic diarrhea in susceptible individuals in high dosages Free fructose, high fructose corn syrup (~50%), sucrose

Types of Carbohydrate

 Glucose Polymers – Short polymers of glucose » Partial hydrolysis of starch – – Soluble, low osmolarity, rapid gastric emptying, digestion, and absorption Most, but not all studies, suggest that glucose polymers may be superior to glucose, fructose, and sucrose

Types of Carbohydrate

 Solid vs Liquid Carbohydrates – – Most studies suggests little difference between solid vs liquid carbohydrates » Those that show difference tend to suggest that liquids are more rapidly absorbed Ultra-endurance athletes may develop aversion to liquid sweet carbohydrates

Types of Carbohydrate

 Low Glycemic Index Food – – Slowly absorbed resulting in lower, but prolonged elevation of blood glucose Research findings vary when comparing hi-, mod-, and low- GI foods and performance

Types of Carbohydrate

 Individualize type of carbohydrate used – – – Individual differences Sport differences Use before/during workouts » Note outcomes

Carbohydrate Loading

 Theory:   Glycogen depletion is a cause of fatigue in endurance athletes.

Increasing glycogen stores above normal levels will enhance performance in endurance athletes.

Diet, muscle glycogen, and endurance performance.

Karlson & Saltin. J. Appl. Physiol. 1971-31:203-206.

    Subjects: Trained distance runners Protocol: normal vs high carb diet Performance test: 30km run Outcomes: – Muscle glycogen after hi-carb diet was double that than after normal diet – – All runners finished 30km faster after hi-carb diet by an average of 8 minutes No benefit seen in first hour of run, but able to maintain pace toward end of run.

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Carbohydrate Loading Protocol: Classic Method

Depletion Phase (3-4 days)

– Strenuous endurance training – Very low carbohydrate diet 

Repletion Phase (3-4 days)

– Tapered training --> rest – Very high carbohydrate diet » 8-10g CHO/kg

Carbohydrate Loading Protocol: Classic Method: Drawbacks

 High level of fatigue during depletion phase   May result in hypoglycemia and ketoacidosis during depletion phase (nausea, fatigue, dizziness, irritability) Very unusual diet during depletion phase – Unappetizing – May cause GI distress

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Carbohydrate Loading Protocol: Classic Method: Drawbacks

May not result in substantially higher glycogen levels than Modified Method – – Effect of different dietary CHO plans and muscle glycogen content (Sharman, 1981) » Protocol: trained runners, 73% VO2max for 90, 40, 40, 20, 20, 0 minutes Muscle glycogen content » » » 50% CHO diet for 6 days: 160 mmol/kg 50% CHO for 3 days, 70% CHO for 3 days: 203 mmol/kg 15% CHO for 3 days, 70% CHO for 3 days: 207 mmol/kg

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Carbohydrate Loading Protocol: Modified Method

Mild Depletion Phase

– – Normal training with tapering Moderate carbohydrate diet (~4gCHO/kg BW) 

Repletion Phase

– – Light training --> rest Very high CHO diet » » » 8-10gCHO/kg BW 400-700gCHO/day 70-80% of total Calories

Carbohydrate Loading

  Diet a mixture of complex and simple carbohydrates to maximize liver and muscle glycogen Effect of Dietary CHO-type on Rate of Glycogen Synthesis (Costill, 1981) – Protocol: trained endurance athletes, 10 mile run @ 80% VO2max + five 1-minute sprints with 3 minute rests – Muscle glycogen content » 24 hours  High simple CHO diet: 133 mmol/kg »  48 hours  High simple CHO diet: 145 mmol/kg  High complex CHO diet: 138 mmol/kg High complex CHO diet: 165 mmol/kg

Carbohydrate Loading

 Concerns: – – – 2-3 lbs of weight gain (water) » » » 3 grams of water for every extra gram of glycogen stored   300-400 grams of glycogen = 900-1200 grams of water 1.2-1.6kg weight gain (2.5-3.5 pounds) stiffness hyper-hydration nausea and diarrhea with diet changes Useful ONLY FOR ENDURANCE ATHLETES! (events over 60 minutes)