Nutrition Strategies:
Carbs and Fats fuel moderate-intensity exercise, whereas carbs dominate at high aerobic activity
Fat fuels low intensity exercise
Endurance training increases fat oxidation capability, sparing glycogen in the muscles
Sources of carbs during exercise are blood glucose, muscle and liver glycogen, glucose from gluconeogenesis in the liver and carbs consumed during exercise.
Fat is available from intramuscular triglycerides as well as adipose tissue.
Per the USDA and US Department of Health and Human Services recommend:
* 45-65% carbohydrates in the diet
* 10-35% protein in the diet
* 20-35% fat in the diet (No more than 10% being saturated)
Food pyramid:
6-11 servings of bread, cereal, rice and pasta
3-5 servings of vegetables, 2-4 servings of fruits
2-3 servings of milk, yogurt and cheese, 2-3 servings of meat, poultry, fish, beans, eggs, and nuts
Sparing use of fats, oils, and sweets
My plate: fruits and vegetables should occupy ~50%,
Glycemic index: tracks blood sugar over 2 hours, eating higher glycemic index foods increases risk for obesity and type 2 diabetes.
Eating several small meals throughout the day evens out blood glucose and insulin levels.
Recommendation is at least 150 minutes of moderate-intensity exercise per week.
Resting VO2 ~3.5 mL of O2 per kg per minute
MET: ratio of the working metabolic rate to the resting metabolic weight
Sleeping: 0.9, Walking slow: 2, Stationary bike (light): 5.5, Jogging 7.0, Jumping rope 10.0
Convert Mets to Kcals: MET for exercise x 1 kcal/kg/hour x body weight (kg) x hours exercised
B-complex vitamins are important in energy metabolism, and athletes require more.
Exercise may increase the need for antioxidants Beta carotene, vitamin C, and vitamin E due to free radicals
Sodium and Potassium are also required in greater amounts
Endurance athletes may require more iron, eating meat is important for iron
* Women athletes may eat less and may get microcytic hypochromic anemia because of this. Same with vegetarians
Protein recommendations:
0.8 g per kg of body weight for sedentary individuals or 0.9 g for vegans/vegetarians
1.2-1.4 g/kg for endurance athletes
1.6-1.7 g/kg for strength athletes
Hydration:
Water lubricates tissues and transports nutrients and other chemicals into, throughout and out of the body.
Water volume maintains blood pressure, and evaporation cools the body
Water loss is 1-2 liters per day
Electrolytes are minerals that circulate in the body and include sodium, potassium, magnesium, calcium, chloride, and phosphate.
* Those lost in sweat are sodium and potassium
* Responsible for the transmission of electrical signals across nerve and muscle cell membranes, and sodium maintains blood volume.
ACSM recommends consuming 14-20 oz of fluid 2 hours before exercising
During exercise lasting more than 1 hour, fluids containing carbohydrates and electrolytes are recommended 20-36 oz per hour, preferably spread out at 15-20 minute intervals.
Postexercise food can replace lost electrolytes and water can be used for hydration, but sports drinks can work in a pinch
Cold increases the water vapor lost through respiration and may increase primary losses
Applications of Nutrition Concepts
Body Composition:
Body Mass Index: Weight (kg) / height (m2) - does not correlate with body fat %
18 - 24.9 Healthy
25-30 Overweight
30-40 Obese
Body composition: Divided into Fat mass and Fat free mass; FM is body fat, FFM is everything else
Fat mass is measured with densitometry, DEXA scan, Bod pod (Air), Bioelectric impedence, Skinfold measurements
* No eating 3-4 hours prior to testing and well hydrated
Lean body mass: Organs, Tissues, Bones, Muscle, includes brain and spinal cord
* Lean body mass = Body weight - Body fat
High body fat risk factor for DM, CVD, Metabolic syndrome (Dyslipidemia, High cholesterol, Tryglycerides), Insulin resistance, and HBP. Also certain cancers and arthritis.
Low body fat risk factor reproductive problems, osteoporosis, and nutrient deficiencies.
Normal body fat percentages: 10-22% for men, 20-32% for women
A waist-hip ratio greater than 0.95 for men or 0.86 for women is considered unhealthy
Waist circumference greater than 40 for men or 35 for women is considered unhealthy
Strength training can increase the resting metabolic rate (RMR) and can increase lean muscle mass
Expend or reduce intake by 3500 kcal to lose one pound of body fat.
Weight Management:
Harris-Benedict equation is used to estimate caloric intake for weight maintenance
Males: RMR = 66 + 13.8 x body weight (kg) + 5 x height (cm) - 6.8 x age
Females: RMR = 655 + 9.6 x body weight (kg) + 1.8 x height (cm) -4.7 x age
* Multipliers: 1.2 bed rest, 1.3 sedentary, 1.4 active, 1.5 very active
Caloric intake = RMR + Thermic effect of food + Exercise expenditure + Energy storage
Sleep deprivation: even 30 minutes per day is associated with insulin resistance and obesity.
Cortisol and ghrelin increase and cause hunger, leptin which shuts down appetite decrease
Endocrine abnormalities like diabetes make weight management difficult. Insulin can lead to storage of excess glucose as fat. When blood glucose is high, exercise reduces that level.
Birth control, Antidepressants and Antipsychotics lead to weight gain due to decreased insulin sensitivity. Metformin also may increase weight gain.
Eating Disorders:
Anorexia: Extreme desire for thinness and fear of gaining weight
* Leads to decreased sex hormone production, as well as amenorrhea, and osteoporosis
* Female athlete triad
* Calcium, Magnesium and Vitamin D supplements may be helpful in ameliorating bone loss
* Diagnostic criteria: refusal to maintain normal BW, fear of being overweight, unreasonably poor body image, amenorrhea
Bulimia Nervosa: Uncontrollable urge to binge followed by compensatory actions, purging, fasting, exercise or using laxatives, enemas, and diuretics
* Diagnostic criteria: Binge eating >2x per day for 3 mo. or more, excessive actions to compensate for intake, unrealistically poor body image
Maximizing Performance:
Sprinters: ATP, and phosphocreatine are the first fuels used
Middle distance runners: Anaerobic glycolysis fueled by muscle glycogen is the main source
At a mile blood glucose and liver glycogen become important and fat from adipose tissue comprises a growing portion of energy.
As much glycogen is depleted it is increasingly important that blood glucose be maintained for aerobic endurance
Pre-race meals should be high in carbs and protein and low in fat and fiber (Carbo-loading) and should be 1-6 hours before the event
4-8 oz of sports drink every 15-20 minutes
Glucose, Sucrose, and Maltodextrin are superior to fructose at maintaining glycogen
Post-race should be high carbohydrates and protein with additional fat
Resistance training hypertrophy is the result of increased fluid/glycogen in the muscle
Increase in size and number of actin/myosin in the muscle fibers.
Increase in muscle thickness occurs during the repair process.
Performance Enhancing Substance:
No evidence that protein intakes higher than 1.2-1.4 for endurance athletes and 1.6-1.7 for strength
Ergogenic aids: substances that are used to improve exercise or athletic performance by improving energy or strength
Anabolic steroids: mimic the action of testosterone
* Risks: mental challenges - irritability, paranoia; acne, swelling of hands/feet, undesirable sex-effects - shrinking testicles; long term use - kidney, liver and heart damage
Diuretics: used to rid body of anabolic steroids in competition
Beta Blockers: slow the heart and calm anxiety, used to improve focus in archers, shooters, or golfers.
* Can lead to blood sugar problems, weakness, and heart failure
Blood doping: artificial increase in oxygen-carrying capacity of the blood for aerobic performance
*Transfusions, Erythropoietin (EPO) - stimulates RBC production, synthetic oxygen carriers, and cobalt chloride - stimulates RBC production
* Can lead to stroke and heart attack since it thickens the blood
* Erythropoietin (EPO) is a peptide hormone composed of amino acids that circulate in the blood and affects the activities of tissues and organs.
- Examples: Insulin, HGH, human chorionic gonadotropin (HCG), Luteinizing hormone
Ergogenic aid abuse signs: mood swings, depression, irritability, acne, male pattern baldness, enlarged male breasts, intramuscular abscesses, increased fatty acids in the blood, high blood pressure, heart problems and in women a deepening of the voice and in increase in facial hair/body hair
Creatine: legal supplement used by athletes and fitness enthusiasts, Phosphocreatine (PCr) is plentiful in muscle and recycles ADP to produce the energy molecule ATP while simultaneously buffering hydrogen ions built up during muscle contraction.
* PCr + ADP + H+ -> ATP + Creatine
Some evidence to support supplementation to improve performance in intense, short-duration events like sprinting and weight lifting. Meat and fish have natural creatine. 20g/day up to 5 days appears to be effective and safe.
Carbohydrate loading: low carbohydrate diet for 3 days followed by 3 days with max carbohydrates leading into the race/event.
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