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Sept 7 - Energy Balance Part 2.doc

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Physical Education and Sport
Scott Forbes

Sept 10 – Energy Balance Continued Body Weight Regulation • 2 individuals with similar food intakes and levels of physical activity may defend different settling points (ex. Different % fat) • There is a definite trend towards a gradual increase in weight across during the adult life span (increase fat and decrease lean mass) • Many central and peripheral factors are involved in the regulation of energy balance • Although generally stable, systematic increase in body with age • Variables assists with body weight that may be regulated: 1.) dietary intake 2.) physical activity 3.) lifestyle factors Energy Balance E in • Kcal ingested • Macronutrients ingested E out • RMR • TEF • TEPA Increased Obesity Risk: Genetics Vs. Environment • Energy surplus (law of thermodynamics) root of all obesity* • Energy intake (E-in) exceeds energy expenditure (E-out) • Diet composition will cause long term changes in body composition only when there is an imbalance in E-in vs. E-out • The statement, “obesity is a disease” is inaccurate because again, regardless of a hormonal or genetic predisposition, energy surplus is the root of all obesity • Diet composition has no effect on body mass as long as energy in equals energy out • So your diet could be made of one macronutrient, and as long as Ein equals Eout, your mass won’t change Nature Vs. Nurture • Although genetics has a strong influence on body fat levels, environment seems to be driving the epidemic • Increased energy intake: large-portioned, fast, energy-dense, inexpensive food • Decreased energy expenditure: jobs and daily living require less physical labour combined with increased opportunity for sedentary activity (TV, video, computers, iphones, ipads) • Its easier to eat energy dense foods and our lives are less energy demanding.. these are some of the causes for the imbalance in energy balance Energy Intake • What is it? Energy (kcal) provided from foods ingested • Kcal is the amount of energy needed to increase 1 g of water by 1 degree Celsius How is it measured? • Direct calorimetry: Burn food in the bomb calorimeter and see the increase in water temperature • Computer software (food processor) Energy Intake • Total Kcals ingested is the most important factor in energy intake Sources of kcals 1 kcal = 4.185 kJ (4185 J) 1 MJ = 239 kcal CHO: 16.7 kJ/g (4 kcal/g) FAT: 38.1 kJ/g (9 kcal/g) Pro: 16.7 kJ/g (4 kcal/g) Ethanol: 29.3 kJ/g (7 kcal/g) – decrease substrate oxidation Alcohol causes immediate oxidation of itself when it is consumed Remember, most meals we eat are mixed fuels! Macronutrient Intake.. Does it matter • Dietary fat is the macronutrient that makes it hard to maintain energy balance • Dietary fat is considered lipogenic (high energy density, metabolic efficient, palatable, but not satiating – means that it taste good, but doesn’t make you want to stop eating) • leads to hyperphagia (overeating or overconsumption) • other macronutrients (including alcohol) elicit powerful autoregulatory adjustments in their oxidation in response to alterations in intake • fat doesn’t do this.. it leads to easy deposition • If you eat fat, you will be fat Energy and Nutrient Balance Equations Required For Long-Term Weight Maintenance 1.) Energy Balance Rate of energy input (Dietary energy + Stored Energy) = Rate of energy expenditure 2.) Nutrient Balance Rate of protein intake = rate of protein oxidation Rate of fat intake = rate of fat oxidation Rate of carb intake = rate of carb oxidation Rate of alcohol intake = rate of alcohol oxidation Insulin is one of the key factors that helps to break down glucose and carbs • No perceptible differences in total daily energy expenditure over a range of diets containing 10% fat to 80% fat (energy balance maintained). • When excess energy is consumed, di
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