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NFS284 Chapter 7 Review Notes

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Nutritional Science
Tom Wolever

Nutrition: Science and Applications  Circulation in the blood Chapter 7 – Energy balance and weight management  Bound to SHBG  less bioavailable  less stimulation of cell growth Body mass index (BMI) = weight / height 2  Not bound to SHBG  free estrogen  more - Underweight: <18.5 bioavailable  more stimulation of cell growth - Normal: 18.5-24.9 - Overweight: 25.0-29.9 - Obese: >30 - ↑ BMI = ↑ risk of mortality - ↓ BMI = ↑ risk of mortality Obesity epidemic (e.g., globesity) - 60% of Canadians are overweight and obese (BMI >25) - ↑ BMI = ↑ risk of disease relative to healthy body weight (e.g., high blood pressure, diabetes, heart disease) Consequences of obesity - Type 2 diabetes, cardiovascular disease, colon cancer, breast cancer, joint disorders, gall bladder disease, sleep apnea Obesity and cancer - Cancer - Prospective cohort studies (observational studies = association) o Characterized by a series of genetic mutations that result in a cell that: o ↑ BMI = ↑ colon cancer risk o ↑ BMI = ↑ breast cancer risk  De-differentiates  no longer functions as intended Obesity and other diseases  Becomes proliferative  uncontrollable growth; does not respond to stop signals - Gall bladder disease o Excessive production of cholesterol in the liver  Cannot repair damaged DNA  perpetuates genetic mutations o Deposition of solid cholesterol in the gall bladder  Becomes resistant to programmed cell death (e.g., o Also a consequence of rapid weight loss  Rapid loss of body fat increases cholesterol synthesis apoptosis)  Apoptosis = method used by the body to get rid - Sleep apnea o Interruptions of breathing during sleep of damaged cells it cannot repair o Poor sleep and excessive fatigue during the day o Normal colon epithelium  single mutated cell  small tumour  large tumour  malignancy o Fatty tissue in neck compresses the airway and blocks airflow - Joint disorders o Metastasis = spread of cancer from one part of the body to other o Osteoarthritis parts of the body - Cancer development  Breakdown of cartilage that cushions the joints  Increased risk with obesity because weight puts excessive o Insulin and estrogen are growth factors that promote cell growth, pressure on joints resulting in tumour development o Insulin - Gout o Uric acid deposition in the joints  Stimulates the growth of colon cells  Suppresses apoptosis o Increased risk with insulin resistance and obesity Physiological and social consequences of obesity o Estrogen - Weight stigmatization  negative attitudes, mistreatment and  Stimulate the growth of breast tissue  Stimulates the growth of breast tumours (in post- discrimination based on weight status - 90% of people who attempt weight loss fail menopausal women) Energy balance - Thermic effect of food (NEF) or diet‐induced thermogenesis - Energy content consumed (food) = Energy content expended (metabolism, o 10% of TEE PA)  weight is unchanged (energy balance) o Increase in body temperature after eating - Energy content consumed (food) > Energy content expended (metabolism, o Energy required for the digestion, absorption and storage of PA)  weight gain (positive energy balance) nutrients o Most people are in a very small positive energy balance, so weight  Fat = 2-3% of energy consumed gain is very gradual  Carbohydrates = 6-8% of energy consumed - Energy content consumed (food) < Energy content expended (metabolism,  Protein = 15-30% of energy consumed PA)  weight loss (negative energy balance) Energy stores Determining the amount of energy (Kcalories) in food - Glycogen (source of glucose) is found in liver and muscle - Combustion in a bomb calorimeter gives the total energy content of food - Glucose or FFA is found in body fluids o Bomb calorimeter  rise in the temperature of water used to - Triglyceride (source of fatty acids) is found in adipose tissue calculate the energy content of food - Protein (source of amino acids) is found in muscle - Correct for unavailable components of food (e.g., dietary fibre) - Using body stores (weight loss) - Results o When you haven’t eaten in a while, then you retrieve energy from o Carbs = 4 kcal/g body stores o Protein = 4 kcal/g o Used when intake is less than needs (e.g., between meals, o Alcohol = 7 kcal/g starvation, fasting, dieting) o Fats = 9 kcal/g o If energy stores are not replenished, the amount of stored energy Converting food energy into ATP (and body weight) will decrease - Glycolysis converts glucose to pyruvate, which is then converted to acetyl o Protein is not stored in the body CoA  Breakdown of protein into amino acids to provide energy - Beta‐oxidation breaks fatty acids down to acetyl CoA and to synthesize glucose (gluconeogenesis) results in - Deamination of amino acids the loss of functional body proteins - Breakdown products of glucose, fatty acids, and amino acids enter the - Building body stores (weight gain) citric acid cycle o Hierarchy of nutrient use - Energy from electrons are used to make ATP  Alcohol Total energy expenditure (TEE)  Rapidly oxidized to avoid toxicity - Basal metabolism  Protein o Energy required to involuntary processes needed to support life  Synthesize body proteins o Expressed as basal metabolic rate (BMR) (kcal expended/unit Used as energy time)  Carbohydrate  Decreases with weight loss  Maintain blood glucose levels  Adaptation to starvation  Build glycogen stores o 60‐75% of TEE  Oxidized for energy o Measured in AM, warm room, before subject rising, 12 hours  Fat without food or exercise  Oxidized for energy - Physical activity  Stored in as triglycerides In adipose tissue o 15‐30% of TEE o Voluntary activities of daily life and planned exercise o Non‐exercise activity thermogenesis (NEAT)  Heat generated by non-intentional exercise (e.g., fidgeting) o Storing kcalories as fat - Satiation  feeling of fullness that develops DURING a meal  Synthesizing triglycerides for storage from carbohydrates o Determines when a meal will end and protein are minor contributions because Regulation of energy balance energetically costly - Body characteristics are inherited from parents  Synthesizing triglycerides from fatty acids (and glycerol) - Obesity genes is a major contribution o Regulation of:  Stored triglycerides reflect the fatty acid composition of  Food intake the diet  Energy expenditure Guidelines for a healthy body weight  Fat metabolism - Healthy body weight depends on - Set point theory o Absolute weight o Genetically pre-determined body weight o % body fat o Tends to be defended o Location of fat  After any type of weight loss, people tend to return to  Visceral fat (mostly men)  apple-shaped their pre-weight loss weight  ↑ health risk  High & unhealthy weight to healthy weight is the same as healthy weight to low & unhealthy weight  ↑ risk of T2D and heart disease  ↑ FFA release  Our physiology only detects weight change  ↑ insulin resistance Short term regulation (e.g., meal-to-meal intake) - Stimulate hunger  ↑ inflammation  Subcutaneous fat (mostly women)  pear-shaped o Ghrelin - Lean tissue  Secreted by the stomach o Fat-free mass (e.g., muscle, bone, all tissues except fat)  Stimulates eating at set times - Fat tissue  Before a meal  ↑ ghrelin levels in the blood  stimulate hunger o Women have more % body fat than men o % body fat increases with aging  After the start of a meal  ↓ ghrelin levels in the blood o Sarcopenia  loss of muscle with aging  reduce hunger - Suppress hunger - Methods to assess a healthy body weight o BMI o Cholecystokinin (CCK)  Most common assessment tool for assessing healthy  Released when chyme enters the small intestine from the stomach body weight  Limitations  Suppresses food intake  Correlates well with % body fat but not perfect o PYY  Suppresses food intake  High % lean body mass  high BMI  Not suitable for use in pregnant and lactating o GLP-1  Stimulates the release of insulin women  Used in combination with waist circumference  Suppresses food intake o Waist circumference - Obese individuals
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