Nutrition

Understand the limitations of knowledge of nutrition

 

Scope of practice

  • As a fitness professional or exercise world

    • Can provide advice on what constitutes a health diet for the gen population

    • Can not prescribe diets or supplements to treat medical conditions

 

Why nutritional advice varied and contradictory

  • Food is complex

  • Exercise affects the food-physiology interaction

  • Way food is grown is very different

    • Different conditions and soils can change nutrition levels

  • Nutritional information is contradictory

  • Dose-response relationships are poorly understood

    • Too much of a good thing exists

  • A lot of advice is contrary to evolutionary logic

  • Manufacturers make unreliable calims

    • Fat free might include more simple sugars in it

  • Nutritional guidelines aren't always objective

 

What we do know

  • Theres no single optimal diet

  • Foods highly processed, high-fructose corn-syrup, trans fats, large amounts of sugar, refined flours, industrially produced fats appear to be problematic

    • Turns liquid fats to solid fats, margarine

    • Fats become hydrogenized

  • Traditional diets low in processed foods appear to be better

 

 

Define nutrition and know the basics of macronutrients

 

Nutrition

  • Relationship between physiological function and elements of food

 

Macronutrients

  • Need in large amounts

  • Carbs, fats, protein

 

Micronutrients

  • Need in smaller amounts

  • Vitamins, minerals

 

Essential Nutrients

  • Carbohydrates

    • 4kcal/g

    • Supply energy to cells in brain, nervous system and muscles

    • Simple vs complex

      • Simple is monosaccharides, easy to digest, added sugar in baking or coffee. Also found in grains and fruits

      • Complex is polysaccharides, many sugars combine together, longer to digest. Feel fuller for a longer time. Glycogen

  • Proteins

    • 4kcal/g

    • Form important parts of muscles, bone, blood, enzymes, call membranes

      • Repair tissue, regulate water, helps in growth

      • 20 amino acids

  • Fats

    • 9kcal/g

    • Supply energy , insulate, support and cushion

  • Vitamins

    • Promote (initiate or speed up) specific chemical reactions within cells

  • Minerals

    • Helps regulate body functions, aid in growth and maintenance of body tissue, act as a catalyst for release of energy. Seen in hormones

  • Water

    • Provide a medium for chemical reactions, transports chemicals, regulate temperatures and remove waste products

 

 

 

Understand how diet fuels exercise and how intensity plays a role

 

Fuel for exercise

  • Carbohydrates and fatas are major fuels used during exercise

  • Under typical circumstances muscles have 4 major sources of energy

    • Plasma (blood) glucose

    • Muscle glycogen

    • Intramuscular triglycerides

    • Plasma fatty acids

 

Blood glucose

  • Always needs to be maintained

  • Regulated by hormones like insulin and glucagon

  • After a meal blood glucose is higher

    • Liver removes the glucose from the blood and stores it as glycogen by insult

    • If glycogen stores are full excess blood glucose is stored as fat in adipose tissues

  • Between meals and during exercise blood glucose decrease

    • Liver releases stored glycogen to be broken down to glucose

    • Lactate produced during exercise is converted to glucose for fuel during exercise

 

Muscle Glycogen

  • The use of glycogen during exercise by a specific muscle depends on

    • Specific muscles involved in the exercise

      • Glycogen will be depleted in the muscles used

 

  • Exercise intensity

    • Higher percentage of VO2 max equals an increased use of glycogen

  • Type of muscle fibre or motor unit recruited

    • Depends on exercise intensity

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When you don't have enough glucose

  • Glucose supplied to muscle cells from blood glucose or msucle glycogen has a orle in protein sparing

    • If you don't have enough glycogen for muscular contractions, the muscle can convert amino acids into glucose thorugh a process of gluconeogenesis

 

Gluconeogenesis

  • Generation of glucose form non-carbohydrate substates like lactate, glycerol and some amino acids

  • Cat cannot be converted into carbohydrate

 

Fat as fuel

  • Intramuscular triglycerides (in muscle) and plasma fatty acids (in blood)

 

  • Glycogen store in the body aren't large and can be depleted in endurance events

    • Fait is another main energy source

 

  • Low intensity event primarily use stored fat in adipose tissue released as plasma fatty acids

  • As intensity increases, higher contribution from intramuscular triglycerides

  • As intensity increase, higher contirbution from intramuscular triglycerides

 

Protein

  • At rest protein isnot primary energy source

  • If needed protein will be broken down via gluconeogensis

 

Fuels

  • Factors that govern the selection of fuels for exercise

  • Intensity of endurance exercise

    • At rest, 2/3 or ATP production from fatty acids, 1/3 come grom glucose and glycogen

    • At 95% of VO2 max, carbohydrate is used almost exclusively

  • Duration of endurance exercise

    • 65-85% of VO2 max it takes 80-120 mins to deplete muscle glycogen

    • As exercise increases, the proportion of energy produced from fat begins to increase

 

  • As intensity increase, we used more glucose and glyogen as energy

    • More available, faster to create

  • As intensity lower, we use more fats

  • Type 2 fibres

 

 

 

 

 

Understand the impacts of ingesting carbohydrates for endurance events

 

 

  • We still use carbohydrates at low intensity and long duration is just the difference of proportions

 

Fitness and fuel

  • Those who are more aerobically fit will exercise at a lower percentage of their vO2 max than someone who is less aerobically fit

    • Cardiac out put

    • Efficiency of A-VO2 diff

  • Endurance training increases the number of mitochondria and aerobic enzymes in train msucle fibres

    • Allowing someone who is aerobically fit to get a greater proportion of energy from fat at any given % of VO2 max compared to someone who is less aerobically fit

    • Those who are aerobically fit rely less on the carbohydrates and glycogen sotres

 

Dietary Carbohydrates and lgycogen stores

  • Amount of carbs in the diet affects th amount of glycogen stores in muscle fibres

    • All other factors being equal, those who are on high-carb diet will have higher muscle glycogen levels

  • Don't start an endurance race with deplete glycogen stores

    • Training with low carbo availability can improve the body's ability ot metabolize fats

      • Important for endurance race to to limited availability of glucose

 

Carbs and Work time

  • Those who have low carb diet aren't able to work as hard

  • Those with high diet were able to work the hardest

    • More carbs means more exercise you can complete

 

Carbs and Exercise

  • Simple carbohydrates prior to exercise will increase insulin

    • Insulin will trigger your body to remove blood glucose to maintain normal blood glucose levels

      • Will create a crash when we exercise

      • Not having

        simple carbs before will prevent crash

    • Complex carbohydrates will raise blood glucose levels more slowly

  • Glucose feeding during exercise is essential in long endurance activities

    • Increase blood glucose levels and icnrease performance

    • Exercise activates the sympathetic nervous system (fight or flight mode) and supresses insulin and maintain blood glucose levels

  • Simple carbohydrates can help refuel glycogen stores after exhaustive exercise

    • A recommendation of 1.5g of carbs per kg of body weight within 1 hour after a hard workout