Chapter 17 Nutrition
- Know all Definitions throughout the chapter
- Table 17.4 Know all of the Essential Amino Acids
- Table 17.6 Recommended Protein Intake
- Daily recommendations for fiber
- Specific recommendations for endurance athletes
- Fatty acids
- Lipids in the body
- Daily recommendations and importance of water
- Table 17.11The effects of dehydration
- Be familiar with guidelines for altering body composition
- Risks of very low calorie diets
- Calorie count for proteins, carbohydrates, fats
- Nutrition – Process by which living organism assimilates food and uses it for growth and repair of tissues.
Standards of Practice and Scope of Practice: Personal Trainers versus licensed Dieticians
- Should be familiar with concepts of nutrition.
- Professional, legally qualified to practice in the field of nutrition is Registered Dietician(RD). RD is specialized in food and nutrition expert with extensive training.
- Practice of nutrition is governed by national credentialing programs and state licensing laws. 46 states have specific laws that explicitly define scope and practice for nutrition and dietetics professionals, and performing these duties without a license could be considered illegal.
Daily Energy Needs
- Calorie – amount of heat energy required to raise temp of 1 gram of water 1C.
- Calorie – Unit expression of energy equal to 1,000 calories. Amount of heat energy required to raise 1 KG or liter of water 1C or kilocalorie.
- Kilocalorie – equal to 1,000 calories, raise 1kg of water 1 degree C.
- Estimated total energy expenditure(TEE) is defined as amount of energy(calories) spent, on average, in a typical day. TEE the sum of three different energy components:
- Resting metabolic rate(RMR) 70% of TEE., Thermic effect of food(TEF) amount of energy expended above RMR as a result of processing of food, TEF typically accounts for 6-10% of TEE. Energy expended during physical activity – Approx 20% of TEE.
Resting metabolic rate
- Accounts for 70% of total daily energy expenditure in sedentary person. Affected by wide variety of factors including age, sex, genetics, hormonal changes, body size, body comp.
- 27 million Americans have thyroid related disorders.
- Cardiovascular meds can reduce RMR from 4 to 12%. Chemo can reduce RMR from 6 to 11%. Long term use of growth hormone increases RMR by 12%. Thyroid meds and hypothyroidism can increase RMR by 17%.
- Thermic effect of food – Process of digestion requires energy, increase in energy expenditure after meal is called thermic effect of food (TEF) 6-10% of total energy expenditure.
Estimating Total Daily Energy Expenditure
- Weight(lbs) x 10 = RMR
- RMR x activity factor = TEE
- Even most commonly used formulas can have up to 20% variance in over or understimating resting metabolism and total energy expenditure.
- Protein – Amino acids linked by peptide bonds. Build and repair body tissues and structures. Involved in synthesis of hormones, enzymes, and other regulatory peptides.
Structure of Protein
- Made up of amino acids linked together by peptide bonds. Body uses approx 20 amino acids to build its many different proteins. Arranging amino acids in different sequences yields the body’s myriad of proteins.
- Two general classes of amino acids: essential and nonessential.
- Essential amino acids cannot be manufactured in the body – therefore must be obtained from food supply or some other exogenous source.
- Nonessential – body can manufacture them from dietary nitrogen and fragments of carbs and fat.
- Arginine and histidine are semiessential amino acids.
Digestion, Absorption, and Utilization
- Proteins must be broken down into constitutent amino acids before body can use them or repair tissue or as energy substrate. Fate of amino acids after digestion depends on body’s homeostatic needs, which can range from tissue replacement or tissue addition to need for energy.
- Proteins encounter HCL in stomach which uncoils(denatures) protein so that digestive enzymes can begin dismantling peptide bonds. The enzyme pepsin begins to cleave protein strand into smaller polypeptides(strands of several amino acids) and single amino acids.
- As protein fragments leave stomach and enter small intestine, pancreatic and intestinal proteases(protein enzymes) continue to dismantle the protein fragments.
- Resulting dipeptides, tripeptides, and single amino acids are then absorbed through the intestinal wall into enterocytes and released into the blood supply to the liver.
- Once in bloodstream, free-form amino acids have several possible fates: they can be used for protein synthesis(building and repairing tissues or structures), immediate energy, or potential energy(fat storage).
- Amino acids are first deaminated(stripped of amine group), allowing remaining carbon skeleton to be used for production of glucose or ketones to be used for energy. Removed amine group produces ammonia, which is converted to urea in the liver and excreted as urine by the kidneys.
- If intake exceeds need for synthesis, then proteins are deaminated, carbon fragments stored as fat.
Protein in Foods
- If food supplies all essential amino acids in appropriate ratios it is called complete protein. If food source is low or lacking in one or more essential amino acids it is called incomplete protein.
- Biologic value (BV) measure frequently used when discussing protein sources, BV is measure of protein quality, how well it satisfies body’s essential amino acid needs.
- Protein source with higher score provides amino acid profile that is more closely related to needs of the human body.
- Major sources of complete proteins are animal sources, dairy and meats. Sources of incomplete protein include grains, legumes, nuts, seeds, and other vegetables.
Negative Energy Balance
- During negative energy balance amino acids are used to assist in energy production, a term called gluconeogenesis. Depleted glycogen increases gluconeogenesis. Supported by released of amino acids from structural proteins to maintain glucose homeostasis.
Protein’s Effect on Satiety
- More satiating than fat or carbs. Studies indicate protein has direct effect on satiety.
Protein Intake Recommendations
- Recommended Daily Allowance(RDA) for protein is 0.8 g/kg/day. 10 to 35% of total caloric intake.
- High protein diet defined as higher than 35%. Risk factor for heart disease and some types of cancer.
- Carbohydrates – Neutral compounds of carbon, hydrogen, and oxygen(such as sugars, starches, and celluloses), which makes up a large portion of animal foods.
- Sugars(simple), starches(complex), and fiber. Monosaccharide is single unit of sugar, many of which are connected to make starches. Monosaccharides include glucose, fructose, and galactose.
- Disaccharides(two sugar units) include sucrose(or common sugar), latose(or milk sugar), and maltose.
- Polysaccharides are long chains of monosaccharide units linked together and found in foods that contain starch and fiber. Called complex carbohydrates and include starch found in plants, seed, and roots.
- Dietary fiber is part of plant that cannot be digested by human gut enzymes and passes through small intestine and colon.
Digestion, Absorption, and Utilization
- Simple sugars are very easily digested. Double sugars such as table sugar require some digestive action but are not nearly as complex as starches. Starches require prolonged enzymatic action to be broken down into simple sugars.
- Rate at which ingested carbs raise blood sugar and its accompanying effect on insulin release is referred to as the glycemic index(GI).
- Mixed meals or protein, carbs, and fat can alter the glycemic effect of single foods.
- All carbs are eventually converted into simple sugars such as glucose or fructose.
Role of Fiber in Health
- Higher fiber intake is associated with lower incidence of heart disease and certain types of cancer.
- Insoluble fiber does not absorb or dissolve in water. It passes through the digestive tract close to its original form. Insoluble fiber offers many benefits to intestinal health, including a reduction in the risk and occurrence of colorectal cancer, hemmrrhoids, and constipation.
Carbs and Performance
- As duration of activity increases, available glucose and glycogen diminish. Increasing reliance on fat as fuel source.
Carbohydrate Intake Performance
- 6 and 10g/kg/day of carbs is recommended. 45 to 65% of total caloric intake. Complex carbs constitute majority of calories.
- Before exercise consume high carb meal 2 to 4 hours. Glycogen stores are lowered by as much as 80% in the mornings.
- Endurance athletes consume between 30 and 60g of carbs every hour to maintain blood glucose levels.
- One hour of intense cycling was improved by 12% with consumption of 53 ounces of water containing 79g of carbs.
- Timing of carbs important for maximizing recovery, recommended consuming 1.5g per KG of carbs within 30 mins of completing exercise to maximize glycogen replenishment. Delaying intake by even 2 hours can decrease total muscle glycogen synthesis by 66%. PWO environment hasten glycogen repletion as a result of increased blood flow to muscles and increased sensitivity of cells to effects of insulin.
- Lipids – Group of compounds that includes triglycerides(fats and oils), phospholipids, and sterols.
- Saturated or unsaturated. Unsaturated classified as monounsaturated or polyunsaturated.
- Polyunsaturated provide important essential fatty acids(fats that cannot be manufactured by the body but are essential for proper health and functioning).
Function of Lipids
- Lipids(or fats) are most concentrated source of energy in the diet. One gram of fat yields approximately 9 calories when oxidized.
- Fats act as carries for fat-soluble vitamins A, D, E, and K. Vitamin D aids in absorption of calcium. Fats are also important for conversion of carotene to vitamin A.
- Fats are involved in: cellular membrane structure and function, precursors to hormones, cellular signals, regulation and excretion of nutrients in cells, surrounding protecting and holding in place organs, insulating body from environmental temp changes, prolonging digestive process by slowing stomach’s secretion of HCL, longer lasting feeling of satiety, initiating release of hormone cholecystokinin(CCK) which contributes to satiety.
Digestion, Absorption, and Utilization
- Fat becomes emulsified in intestine so that pancreatic enzymes can break triglycerides down into two fatty acids and a monoglyceride. These are absorbed through intestinal walls into blood.
- In intestinal wall they are reassembled into triglycerides that are then released into the lympth in the form of lipoprotein called chylomicron. Chylomicrons from the lymph move to the blood. Triglyceride content of chylomicron is removed by action of the enzyme lipoprotein lipase (LPL), and the released fatty acids are taken up by the tissues. Throughout the day triglycerides are constantly cycled in and out of tissues, including muscles, organs, and adipose.
- 20 to 35% of total calories from fat.
- Dietary fats stimulate release of CCK, hormone that signals satiety. Fat slow digestion of foods and thus nutrient content in the bloodstream.
- Medium chain triglycerides are more rapidly absorbed, they do not require incorporation into chylomicrons for transport but can enter systemic circulation directly providing readily avaialble, concentrated source of energy. MCT could benefit endurance performance by suppling exogenous energy source in addition to carbohydrates during exercise and increase plasma free acids(FFA), sparing muscle glycogen.
- Sedentary men and women should consume 3L (13 cups) and 2.2L(9 cups) of water per day. Those in fat loss programs should drink additional 8 ounces of water for every 25 pounds they carry above their ideal weight. Water intake should be increased if individual is exercising briskly or residing in a hot climate.
- 60% of adult human body by weight.
- Benefits of consuming adequate water: endocrine gland function improves, fluid retention is alleviated, liver functions improve, natural thirst returns, metabolic functions improve, nutrients are distributed throughout body, body-temperature regulation improves, blood volume is maintained.
- Fluid loss of 2% of body weight will adversely affect circulatory functions and decrease performance levels. Thirst alone is poor indicator of how much water is needed.
- Athletes consistently consume inadequate fluid volume, managing to replace only 50% of sweat losses. Do not being practice session or endurance comp until body is at or slightly above standard weight.
- Drink 1.75 to 2.75 cups 2 hours before exercise. Drink 6 to 12 ounces of fluid every 15 to 20 minutes. Fluids should be cold because of more rapid gastric emptying.
- If exercise exceeds 60 mins use sports drink(containing up to 8% carbohydrate).
- When exercising for less than 60 minutes, water is experts’ choice for fluid replacement
- Ingest 16 to 24 ounces of fluid for every pound of body weight lost after an exercise bout, especially if rapid rehydration is necessary, as in twice-a-day training.
Altering Body Composition
Basic nutritional guidelines for altering body composition for fat loss
- Small decreases in food and beverage calories and increase physical activity.
- Distribute protein, carbs, and fat throughout day.
- Consume less than 10% of cals from saturated fat.
- Choose whole grains and fiber rich fruits and veggies over refined grains and simple sugars.
- Limit alcohol.
- Schedule no fewer than four and as many as six meals a day.
- Avoid empty calories and highly processed foods.
- Drink plenty of water(minimum 9 to 13 cups a day)
- Have clients weigh and measure food at least 1 week. Make them more aware of caloric values and serving sizes.
For lean body mass gain
- 4-6 meals a day. Spread protein intake throughout day.
- Post workout window of opportunity, ingestion of proteina nd carbs within 90 mins of a workout will increase recovery and protein synthesis, maximizing gains.
- Do not neglect importance of carbs and fat.
Risks of Starvation(low cal) Diets
- Nutrition experts do not recommend energy intake lower than 1,200 calories.
- Increased risk of malnutrition, poor energy and inability to complete essential fitness program, behavioral pendulum swing, minor side effects as fatigue, constipation, nausea, diarrhea. Gallstone formation.