Notes About Nutrition by John Josephs, MS
Filed under:
Carbohydrate (Carbs) are without question the most important food fuel source to replace during exercise less than 1 hour.
Fat is the most efficient fuel source — you derive more energy burning fat as fuel than you do burning carbs.
Oxygen is necessary to metabolize fat for fuel.
Fat is utilized as energy in low intensity, aerobic exercise.
Carbohydrates are stored in the body as glycogen. 78% is stored in the muscle, 18% is stored in the liver, and the rest the rest is available in the blood as glucose.
Individuals can store approximately 1500-2000 calories as glycogen. This means that moderate to high intensity exercise can be maintained for approximately 2 hours before glycogen stores are depleted.
You never burn 100% carbs or 100% fat as fuel. It is always a mixture of these two fuel types. The lower the intensity, the higher % of fat is utilized. As exercise intensity increases, the % of carbs increase and fat decreases.
Ironman = 65% Fat + 35% Carbs
Olympic = 35% Fat + 65% Carbs
Sprint = 25% Fat + 75% Carbs
DIET
There is no magical way to determine the best possible training diet for you. Every athlete is different and you must determine what is best through trial and error in training. Your goal is to find fluid replacement and energy-dense foods that are palatable and fulfill your energy demands.
Energy-dense foods are foods that are high in calories relative to their size and have a high Glycemic Index (GI). Energy bars and gels are good examples of energy-dense foods used by endurance athletes to replace calories and provide continual energy.
Glycemic Index ranks carbohydrate-containing foods according to their instant effect on blood sugar levels. High GI foods educe a fast, blood glucose response. Low GI foods educe a slow, sustained response.
Away from racing and training, athletes who are looking to improve their body composition should avoid additional intake of energy-dense foods and increase their intake of nutrient-dense foods.
One pound of fat equals 3500 calories. Individuals looking to lose weight through diet and exercise should aim for a caloric deficit of 300-500 calories per day.
Never eat or drink anything in a race that you have not previously tried in training.
The best diet is a "well-balanced" diet. Eat mostly lean meats, fish, poultry, shellfish, fresh fruits and vegetables (nutrient-dense foods).
The bottom line of your dietary decisions is the relative mix of four macronutrients: protein, carbohydrates, fats, and water.
FLUIDS
Water is the most common and important nutrient of the body. It accounts for approximately 40 to 70% of our total body weight depending on age, gender, and body composition.
Water is the primary component of blood that transports fuel and oxygen to the working muscles and removes waste products (CO2 & Lactic Acid) from our system.
Losing too much water from exercise without adequate hydration inhibits the body's ability for optimal performance and power output.
Water is essential for regulating body temperature. During high intensity exercise in a hot, humid environment, an athlete may lose 2-3 liters of fluid per hour.
Once we realize thirst, the initial stage of dehydration has started and replacing lost fluid at this point is difficult.
It is important to drink water steadily throughout the day when you are training. Drink 8 to 12 cups per day.
A general rule of thumb is to drink enough water so that you visit the bathroom every 2 to 4 hours and your urine is clear and odorless.
Feeling chronically tired and experiencing frequent headaches could be a sign that you are experiencing dehydration.
Dehydration of only 2% of body weight can effect performance and impair your thermoregulatory ability.
Less fluid means less blood volume. A decrease in blood volume increases heart rate in order to deliver oxygen and nutrients to working muscles. In addition, body temperature will increase. The combination of these factors will lead to a reduction in performance and decrease time to exhaustion.
There is no other factor that impacts performance as quickly and as greatly as your hydration status.
Pace and power decrease by 2% for each percentage of body weight lost to dehydration.
Exercise in hot weather greatly increases the body's water requirement up to 5 or 6 times normal requirements in extreme conditions.
Excessive sweating combined with excessive ingestion of plain water sets the stage for hyponatremia or water intoxication.
SWEAT RATE
Monitoring changes in body weight provides a convenient method to assess fluid loss during exercise.
Check your body weight (in the buff) prior to exercise.
Keep track of all fluid replacement during your exercise session.
Re-weigh yourself immediately following your workout.
Each pound of body weight loss translates into 16-20 ounces of fluid or 1000 ml. for each kg.
Determining your sweat rate is essential in shaping a successful nutritional and hydration plan for endurance training and optimizing your racing strategy.
FATS
1 Gram Fat = 9 Calories
Some type of fats should be avoided or kept at low levels. They are saturated fats, trans fatty acids, and human-made fats found in many processed "hydrogenated" foods.
Good fats are "monounsaturated" and "omega-3." These fats include oils and spreads of almond, avocado, hazelnut, macadamia nut, pecan, cashew, and olive. Other good sources are the oils of coldwater fish such as tuna, salmon, and mackerel.
There are many health benefits associated with eating the right type and amount of fats. They protect vital organs, provide insulation, and transport the fat-soluble vitamins A, D, E, and K.
Fats contribute 50-70% of the energy requirement during light and moderate exercise. Stored fat plays an increasingly important role during prolonged exercise. Aerobic training increases and improves fatty-acid oxidation.
By-products from carbohydrate breakdown help the body's metabolism of fat.
Enhanced fat oxidation spares glycogen, allowing trained individuals to exercise at a higher level of submaximal exercise before feeling the effects of glycogen depletion.
Sensible recommendations suggest an average of 25-30% fat in our diet in which 70-80% should consist of the good "unsaturated" fats.
PROTEIN
1 Gram = 4 Calories
Protein is not stored in the body for potential use. Excess protein will be converted and stored as glycogen and fat.
Performance is dependent on dietary protein because the body is unable to produce all it needs.
Adequate carbohydrate intake helps to preserve tissue protein.
Dietary protein is made up of 20 amino acids used by the body as building blocks for replacing damaged cells.
Most of these amino acids are produced when the need arises, but there are 9 amino acids that the body cannot manufacture. Animal foods are the best way to get these 9 essential amino acids found in eggs, milk, cheese, meats, fish, and poultry.
If your diet is lacking protein, your body will begin to breakdown muscle tissue to satisfy its needs, resulting in "muscle wasting." Protein use for energy reaches its highest level when subjects exercised in a glycogen-depleted state.
These observations support the importance of athletes eating a high carbohydrate diet with adequate energy intake to conserve muscle protein.
There is no general agreement within the nutritional field regarding the recommended protein intake for endurance athletes. For athletes in heavy training, a protein intake between 1.2 and 1.8 g/kg should adequately meet any protein-related nutritional demands.
Your diet should cycle throughout the year just as your training cycles with your periodization plan (See chart). Protein serves as your anchor and should remain constant as fats and carbohydrates change.
CARBOHYDRATES
1 Gram = 4 Calories
Carbohydrates are the primary fuel you body burns for fuel. The quality and type of carbohydrates you consume is critical to fueling the aerobic engine.
The central nervous system requires carbohydrates for proper functioning.
Major sources of carbohydrates include grains, bread, fruit, and vegetables. They provide energy along with a variety of vitamins and minerals. They are considered nutrient-dense by supplying a significant amount of nutrients per calorie.
A high performance diet emphasizes nutrient-dense carbohydrates necessary to maintain muscle glycogen. Foods like whole grain breads and cereals, rice beans, pasta, vegetables and fruits are considered nutrient-dense because they are high in carbohydrates and other nutrients.
By comparison, foods like cookies, candy bars, and donuts are high in fat and contain only insignificant amounts of vitamins and minerals. These are referred to as "empty calories." They provide a quick energy boost but leave the individual feeling tired 30 minutes after ingestion.
Considering the limited glycogen stores, a physically active person's diet should contain approximately 55-65% of calories from carbohydrates, predominately starches from fiber-rich, unprocessed grains, fruits, and vegetables.
Energy expenditure in the Tour de France averages 6,500 calories/day for 3 weeks with daily variation from 3,000 calories on the "rest" day and increasing to 9,000 calories in the mountain stages.
Triathletes can burn between 9,000 and 12,000 calories during an Ironman race. Your goal should be to replace half of these calories during the race through your nutrition and fluid replacement plan.
Individuals involved in intense and long training sessions should consume at least 10 grams (40 calories) of carbohydrates per kg of body weight (lbs/2.2) each day to induce protein sparing and ensure adequate glycogen reserves.
A carbohydrate-deficient diet rapidly depletes muscle and liver glycogen and negatively affects performance.
High intensity exercise for 1 hour decreases liver glycogen by about 55%, whereas a 2-hour strenuous workout almost completely depletes the liver and active muscle glycogen stores.
The need for optimal replenishment of depleted glycogen provides nutritional justification to reduce or taper the intensity of exercise sessions prior to competition.
It takes at least 20 hours to fully restore muscle glycogen after a glycogen-depleting bout of exhaustive exercise.
DIETARY PERIODIZATION
| Carbs | Protein | Fats | |
| Base | 50% | 15% | 35% |
| Build | 60% | 15% | 25% |
| Peak | 65% | 15% | 20% |
| Race | 70% | 15% | 15% |