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Kin110_Chapter 9 Energy Balance & Weight.docx

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Biomedical Physio & Kines
BPK 110
Gina Whitaker

Kin110 Chapter 9 Energy Balance & Weight Approximately 1.5 billion adults are overweight worldwide World is becoming heavier at a rate of ≈ 2.5 pounds per decade 3 out of 5 Canadians are overweight, ¼ are obese Obesity is due to overeating and a lack of exercise Obesity is associated with cardiovascular disease, diabetes II, some cancers, depression, reduced quality of life, arthritis, sleep disorders, higher chronic pain levels Weight is often used to determine health status A healthy weight is one that minimizes health risks Body Mass Index (BMI)-weight in kg / height in m^2 -overweight BMI is between 25-29.9 kg/m^2 -obese BMI ≥ 30 kg/m^2 Using BMI to assess Healthy Weight Does not account for variations in musculature or bone mass What is more important than BMI is having mostly lean body mass (muscle, bone, internal organs) and minimal levels of body fat -body composition So, BMI must be used in combination with other tools in order to assess body composition Body Composition-relative proportions of fat and lean tissue that make up the body -percent of fat relative to total body weight affects health risks Healthy levels Women: 21-32% of total weight Men: 8-19% of total weight Body Weight = weight of fat + lean body mass Methods for Determining Body Composition Skinfold thickness-uses calipers to measure the thickness of the fat layer under the skin at several locations -this technique assumes that the amount of fat under the skin is representative of total body fat but can be inaccurate if not performed by a trained professional Underwater Weighing-the difference between a person’s weight on land and underwater is used to calculate body density -the higher a person’s body density, the less fat they have Air Displacement-measures the amount of air displaced by the body with body weight to determine body density, which is related to body fat mass Bioelectrical impedance-measures how fast an electrical current travelling through the body -it is based on the fact that current moves easily though lean tissue, which is high in water, but slowed by fat however; measurements will vary depending on the amount of water in the body Dual Energy X-ray (DXA)-distinguishes among various body tissues by measuring differences in levels of X-ray absorption Body Fat distribution Subcutaneous fat-adipose tissue under the skin, for example, in hips and legs Visceral fat-adipose tissue around abdominal organs -more metabolically active -associated with higher disease risk Body Fat: Apples vs. Pears Apples carry excess weight around abdomen (higher risk); pears carry fat around lower body Waist circumference is indicative of amount of visceral fat (around organs), waist circumference and BMI often used to determine health risk -if WC > 102cm for men and 88cm for women, increased health risk Energy Balance-the amount of energy consumed in the diet compared with the amount expended by the body of a given period According to the principle of energy balance, for a person’s weight to remain the same, Energy In Calories from Fat (9 kcal/g) Carbohydrates (4 kcal/g) Protein (4 kcal/g) Alcohol (7 kcal/g) Must equal Energy Out (EEE-Estimated Energy Expenditure) Basal Metabolic Rate (60-75%) Thermic Effect of Food (10%) Physical Activity (15-30%)* *most under your control Basal Metabolic Rate The largest component of energy expenditure Rate that energy is used to perform all basic functions in the body under resting conditions Physical Activity Both daily activities and planned physical activity contribute to this component of energy expenditure Daily activities (non exercise components) -accounts for most activity in a day -varies greatly depending on lifestyle, occupation, etc Examples include walking to work, taking the stairs, typing, physically-demanding jobs, fidgeting Planned Physical activity -going to the gym, run, playing soccer, etc Thermic Effect of Food Smallest component of energy expenditure Energy expended for digestion, absorption, metabolism, and storage of nutrients -depends on amount and type of nutrient consumed When Energy In ≠ Energy Out When you eat more than you need When you eat less than you need Canada’s Energy Imbalance 1) Eating More The healthy, lower Calorie choice is often not the easy choice -busy lifestyle means convenience food High Calorie, highly processed foods are often more available and cheaper Also, portion sizes continue to grow and we often get a better deal the more food we buy Knowledge is Power One of the many reasons people may overeat, is that they have no idea how many Calories their favourite foods actually have 2) Moving Less Only 15% of Canadians meet the new recommendations for physical activity Due to -motorized commuting, sedentary jobs, elevators -busy lifestyle leaves less time for active leisure time Storing Excess Calories If you are trying to manage your weight, the primary dietary factor you must regulate is your Caloric Intake We store most excess energy as fat within adipocytes When fat is gained, adipocytes increase in size and number When fat is lost, adipocytes decrease in size alone * You theoretically have a limitless ability to store fat Determinants of Body Size & Shape Genes + Lifestyle choices -study showed that ≈75% of variation in BMI is due to genes and ≈ 25% determined by lifestyle -there are more than 100 known genes that are associated with regulation of body weight -t
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