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Lecture

Notes for Chapter 13 - Nutrition and Physical Activity

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Department
Food Science and Human Nutrition
Course Code
HUN 2201
Professor
All

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HUN: Nutrition and Physical Activity
Exercise, fitness, and health
oFitness reduces the risk of CVD, diabetes, and obesity
oFitness level defined by endurance, strength, flexibility, and body composition
oOverload principle: the more you do, the more you are capable of doing
Cardiorespiratory endurance
oIncreased by aerobic exercise because they strengthen the heart muscle and
increase stroke volume, the amount of blood pumped with each heart beat.
This in turn decreases resting heart rate, because more blood is being
pumped so the heart doesn’t have to work as hard.
oAerobic capacity or VO2 max: maximum ability to generate ATP by aerobic
metabolism
The greater the aerobic capacity, the more intense activity he/she can
perform before a lack of oxygen affects performance.
Muscle strength and endurance
oWeight lifting causes hypertrophy, increase in muscle size…opposite of atrophy
Flexibility
oDetermines range of motion. Stretching has not been shown to reduce injury
oCan be dynamic, involving motion, or static, involving no motion
How exercise affects body composition
oBuilds and maintains muscle
oNot everyone who is fit is thin
oAffected by gender and age; women have more stored body fat than men. If
activity slows, percentage of body fat increases even if body weight stays the
same
How exercise benefits health
oCardiovascular health
Lowers blood pressure, increases HDL cholesterol, reduces risk of heart
attack and stroke
oDiabetes prevention and management
By keeping body fat within normal range, decreases the risk of
developing type 2
Aerobics and strength training can increase sensitivity of tissues to
insulin
oBone and joint health
Weight bearing exercises help bones grow denser and stronger.
Arthritics could benefit, too
oCancer
Regular exercise may reduce cancer risk up to 40%
Breast cancer risk: related to exercise intensity, duration, and age
Colon cancer
oWeight management
Metabolism increase even after activity slows
Basal energy needs increase as lean tissue mass requires more calories
than fat tissue
Slows loss of lean tissue that occurs with energy restriction
oOverall well-being
Endorphins aid in relaxation, pain tolerance, and appetite control. Lower
risk of cognitive decline and dementia, releases muscle tension,
improves sleep patterns, reduces levels of stress hormone cortisol,
raises body temperature
Exercise Recommendations
oMost Americans do not exercise regularly
oDietary guidelines recommend 150 minutes of moderate intensity or 75 of
vigorous aerobic each weak. Also, muscle strength training 2 or more days per
week.
oExercise cannot compensate for extended periods of time in sedentary pastimes
What to look for in a fitness program
oAerobic activity
30-60 minutes per day, should raise heart rate from 60-85% of its
maximum
Maximum heart rate dependent on age
oMen: 220-age
oWomen: 206 x 0.88[age]
Should include warm up and cool down
oResistance exercise
Adults should wait at least 48 hours between training sessions
Each session should include 8-10 exercises, 3 sets o 8-12 reps
Increasing amount of weight improves strength, increasing
number of reps improves endurance
For older adults, neuromotor exercise helps improve balance, agility, and
muscle strength
oStretching
Combination of static and dynamic
Hold positions 10-30 seconds
oRecommendations for children
60 min per day at least 3 days per week
be careful of overtraining syndrome, which involves emotional,
behavioral, and physical symptoms
Exercise and energy metabolism
oATP can be generated I the presence of oxygen by aerobic metabolism, and in
the absence of oxygen by anaerobic metabolism or anaerobic glycolysis.
oHow duration affects metabolism
Instant energy: stored ATP and Creatine Phosphorus
Short-term energy: anaerobic metabolism
Small amounts of ATP stored in muscle…as that is used,
enzymes break down another high-energy compound, creatine
phosphate, to replenish ATP supply and allow activity to
continue. But this only lasts a few seconds, too.
Basically, just ATP storage and creatine phosphate for the first 15
seconds
Creatine phosphate used up, but heart and lungs still haven’t
had a chance to increase oxygen delivery to the muscles.
After 30 seconds, anaerobic pathways operate at full capacity
oTakes place in cytosol
oGlycolysis: breakdown glucose into pyruvate, releases
electrons, produces ATP
oIf oxygen is unavailable, pyruvate and electrons form
lactic acid
Anaerobic metabolism can produce ATP very quickly, but can
only use glucose as a fuel
oMay come from breakdown of glycogen inside muscle or
from glucose delivered via bloodstream [from liver
glycogen or ingestion of carb during exercise]
Predominates during first few minutes of exercise and intense
exercise
Long-term energy: aerobic metabolism
After 2-3 minutes of exercise
Mitochondria: pyruvate produced by glycolysis is converted to
acetyl co-a, which is broken down by the citric acid cycle,
producing CO2, ATP, and releasing electrons
More slow, but more efficient than anaerobic
oCan use fatty acids and amino acids from protein to
generate ATP
Fatty acids come from triglycerides stored in
adipose
Carnitine activates the fatty acids so they can
enter the mitochondria of muscle cells, where
they undego B-oxidation to form acetyl coa, then
metabolized by citric acid cycle
oWhen exercise continues at low to moderate intensity,
aerobic metabolism predominates and fat becomes the
principal fuel source for exercising muscles. If exercise
increases, proportion of energy generated by anaerobic
versus aerobic changes, as well as amounts of glucose
and fatty acids used
How protein is used during exercise
More protein used if
oHow exercise intensity affects metabolism
Amount of protein used increases if:
oDiet does not provide enough energy
oExcess protein is consumed
oNot enough carb is consumed
Amino acids available to the body come from
oDietary proteins
oBreakdown of body proteins

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Description
• HUN: Nutrition and Physical Activity • Exercise, fitness, and health o Fitness reduces the risk of CVD, diabetes, and obesity o Fitness level defined by endurance, strength, flexibility, and body composition o Overload principle: the more you do, the more you are capable of doing • Cardiorespiratory endurance o Increased by aerobic exercise because they strengthen the heart muscle and increase stroke volume, the amount of blood pumped with each heart beat.  This in turn decreases resting heart rate, because more blood is being pumped so the heart doesn’t have to work as hard. o Aerobic capacity or VO2 max: maximum ability to generate ATP by aerobic metabolism  The greater the aerobic capacity, the more intense activity he/she can perform before a lack of oxygen affects performance. • Muscle strength and endurance o Weight lifting causes hypertrophy, increase in muscle size…opposite of atrophy • Flexibility o Determines range of motion. Stretching has not been shown to reduce injury o Can be dynamic, involving motion, or static, involving no motion • How exercise affects body composition o Builds and maintains muscle o Not everyone who is fit is thin o Affected by gender and age; women have more stored body fat than men. If activity slows, percentage of body fat increases even if body weight stays the same • How exercise benefits health o Cardiovascular health  Lowers blood pressure, increases HDL cholesterol, reduces risk of heart attack and stroke o Diabetes prevention and management  By keeping body fat within normal range, decreases the risk of developing type 2  Aerobics and strength training can increase sensitivity of tissues to insulin o Bone and joint health  Weight bearing exercises help bones grow denser and stronger. Arthritics could benefit, too o Cancer  Regular exercise may reduce cancer risk up to 40%  Breast cancer risk: related to exercise intensity, duration, and age  Colon cancer o Weight management  Metabolism increase even after activity slows  Basal energy needs increase as lean tissue mass requires more calories than fat tissue  Slows loss of lean tissue that occurs with energy restriction o Overall well-being  Endorphins aid in relaxation, pain tolerance, and appetite control. Lower risk of cognitive decline and dementia, releases muscle tension, improves sleep patterns, reduces levels of stress hormone cortisol, raises body temperature • Exercise Recommendations o Most Americans do not exercise regularly o Dietary guidelines recommend 150 minutes of moderate intensity or 75 of vigorous aerobic each weak. Also, muscle strength training 2 or more days per week. o Exercise cannot compensate for extended periods of time in sedentary pastimes • What to look for in a fitness program o Aerobic activity  30-60 minutes per day, should raise heart rate from 60-85% of its maximum • Maximum heart rate dependent on age o Men: 220-age o Women: 206 x 0.88[age]  Should include warm up and cool down o Resistance exercise  Adults should wait at least 48 hours between training sessions  Each session should include 8-10 exercises, 3 sets o 8-12 reps • Increasing amount of weight improves strength, increasing number of reps improves endurance  For older adults, neuromotor exercise helps improve balance, agility, and muscle strength o Stretching  Combination of static and dynamic  Hold positions 10-30 seconds o Recommendations for children  60 min per day at least 3 days per week  be careful of overtraining syndrome, which involves emotional, behavioral, and physical symptoms • Exercise and energy metabolism o ATP can be generated I the presence of oxygen by aerobic metabolism, and in the absence of oxygen by anaerobic metabolism or anaerobic glycolysis. o How duration affects metabolism  Instant energy: stored ATP and Creatine Phosphorus  Short-term energy: anaerobic metabolism • Small amounts of ATP stored in muscle…as that is used, enzymes break down another high-energy compound, creatine phosphate, to replenish ATP supply and allow activity to continue. But this only lasts a few seconds, too. • Basically, just ATP storage and creatine phosphate for the first 15 seconds • Creatine phosphate used up, but heart and lungs still haven’t had a chance to increase oxygen delivery to the muscles. • After 30 seconds, anaerobic pathways operate at full capacity o Takes place in cytosol o Glycolysis: breakdown glucose into pyruvate, releases electrons, produces ATP o If oxygen is unavailable, pyruvate and electrons form lactic acid • Anaerobic metabolism can produce ATP very quickly, but can only use glucose as a fuel o May come from breakdown of glycogen inside muscle or from glucose delivered via bloodstream [from liver glycogen or ingestion of carb during exercise] • Predominates during first few minutes of exercise and intense exercise  Long-term energy: aerobic metabolism • After 2-3 minutes of exercise • Mitochondria: pyruvate produced by glycolysis is converted to acetyl co-a, which is broken down by the citric acid cycle, producing CO2, ATP, and releasing electrons • More slow, but more efficient than anaerobic o Can use fatty acids and amino acids from protein to generate ATP  Fatty acids come from triglycerides stored in adipose  Carnitine activates the fatty acids so they can enter the mitochondria of muscle cells, where they undego B-oxidation to form acetyl coa, then metabolized by citric acid cycle o When exercise continues at low to moderate intensity, aerobic metabolism predominates and fat becomes the principal fuel source for exercising muscles. If exercise increases, proportion of energy generated by anaerobic versus aerobic changes, as well as amounts of glucose and fatty acids used  How protein is used during exercise • More protein used if o How exercise intensity affects metabolism • Amount of protein used increases if: o Diet does not provide enough energy o Excess protein is consumed o Not enough carb is consumed • Amino acids available to the body come from o Dietary proteins o Breakdown of body proteins o When nitrogen amino group is removed, remaining carb can be used to make glucose via gluconeogenesis o Endurance exercise increases use of amino acids, and even after, because protein synthesis is needed to build and repair muscle • How exercise intensity affects metabolism o Both anaerobic and aerobic work to provide ATP during exercise  The more intense the activity, the more the muscles rely on glucose  Which fuels are used determines how quickly fatigue will occur • Why high-intensity exercise contributes to fatigue o More anaerobic metabolism, which can only use glucose for fuel  Rapidly depletes glycogen stores, creates lactic acid  Lactic acid NOT a cause of muscle fatigue, however  60-120g glycogen in the liver, used to maintain blood glucose during the day and at night  200-500g glycogen in the muscles • Why low-intensity exercise can continue longer o Relies on aerobic metabolism, which is more efficient and uses both glucose and fatty acids o Glucose CAN still be depleted, however • Why training increases aerobic capacity o Amount of oxygen that can be delivered to and used by muscle cells o Affects proportion of glucose and fatty acids that can be used o Heart becomes larger and stronger, stroke volume increases o Number of capillaries increase, number of red blood cells expands, more hemoglobin and oxygen o Increased ability to store glycogen, increase in number and size of muscle-cell mitochondria  Increased ability of fatty acids to produce ATP, which spares glycogen and delays onset of fatigue  Conditioned athletes can exercise at higher percentage of aerobic capacity before lactic acid begins to accumulate • Energy and nutrient needs for physical activity o Energy needs  Depends on intensity, duration, and frequency  DRIs based on gender, age, size, and physical activity  EER also affected by amount of body fat tissue and limbs in use o Healthy weight loss  .5-2 lb/wk, reduce calories by 200-500/day o Unhealthy weight loss  Diuretics, laxatives, extreme restriction o Suggestions for weight gain  Increase calories by 500-1000/day  Strength training  Most energy needed to fuel muscle growth comes from carb and fat, so lots of protein is unnecessary • Carb, fat, and protein needs • 45-65% carb, 20-35% fat, 10-35% protein • Carbohydrate o Needed to maintain blood glucose during and replace glycogen stores after exercise o Should be complex with natural simple sugars from fruit and milk • Fat o Unsaturated is best. Low-fat isn’t beneficial! • Protein o Not a significant energy source, but needed to maintain and repair muscle tissue o Eating extra protein will NOT produce bigger muscles o Endurance and strength trainers require about 1.2-1.4g/kg • Vitamin and mineral needs o NEEDED FOR ENERGY METABOLISM: oxygen delivery, antioxidant protection, repair and maintenance of body structures o B vitamins  Production of ATP from carbs and fat  B6, folate, and B12 needed to break down glycogen and release glucose, and make hemoglobin  Recommendation for athletes is the same as normal o Antioxidants  Increased oxygen from exercise increases production of free radical that can cause muscle fatigue  Vitamins C, E, B-carotene, and selenium o
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