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HLSC 3P93 (16)
Lecture 4


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Health Sciences
Paul Leblanc

LECTURE 4 – Energy Balance and Body Weight Energy balance • nurture (environment – 75%) • nature (genetics – 25%) • Energy in = energy out Control of food intake • Central control - hypothalamus • Peripheral control  GI neuromuscular (e.g. distension, osmoreceptors, chemoreceptors) • endocrine (e.g. CCK, ghrelin, insulin, glucagon, leptin, adiponectin) Adipose tissue • Storage site for energetically rich fuel • Metabolically active Endocrine organ • leptin – signals a feeling of being full • adiponectin -- glucose production - FFA synthesis Estimating energy needs • equations (e.g. EER, Harris-Benedict) • indirect or direct calorimetry • doubly labelled water (gold standard in free living subjects) Control of energy expenditure • Obligatory -- resting energy expenditure & thermic effect of food • Facultative -- physical activity energy expenditure & thermic effect of food above obligatory (metabolic inefficiencies) Percent Canadians with BMI > 25 – 59% Percent Canadians with BMI > 30 – 23% Percent Canadian Children and Adolescents with BMI > 85th percentile – 29% Obesity – Nature • 12 pairs of identical twins fed 1000 kcal extra each day for 100 days • Study demonstrated -- inter-twin variation & intra-twin similarities • Bouchard et al. 1990 Obesigenic environment – eating habits • fast food, portion sizes, cost and convenience of high energy dense foods • Fat cell development -- adiposity dependent on fat cell size (hypertrophy) and fat cell number (hyperplasia) • Leptin -- don’t produce or respond to leptin (more similar to human obesity) • 70% of children who are obese maintain their higher weight as adults Obesigenic environment – physical activity habits • increase in sedentary activity (“screen time”) Obesity –Treatments • Assessment based on: BMI • presence of co-morbidities (smoking, hypertension, dyslipidemia, insulin resistance, family history of CHD) • Physical activity -- programmed (regular scheduled bouts) • Behaviour therapy -- eliminate negative cues (e.g. don’t grocery shop when hungry) • Nutritional intervention (Ramage et al 2014) o systematic review of studies  overweight/obese male and female adults (BMI>25) o intervention resulted in weight loss - >5% over at least 3 months • Low calorie diet (Ramage et al 2014)  Energy and macronutrients o 1200-1500 kcal/day caloric restriction o specifically a reduction in fat (<30% total caloric intake) o Fibre -- 17 g/1000 kcal (20-25 g) o decrease cholesterol and alcohol o ↑ nutrient density • Low CHO diet o restricted to 3-10% of total kcal o 13% weight loss after 6 months, 4% after 1 year • Very-low calorie diet o energy intake restricted to 400-800 kcal/day o 30-40% weight loss after 6 months, 30% after 1 year Type 1 Diabetes • accounts for 5-10% of all diabetes • Insulin deficiency (lack of insulin production; destroyed pancreatic β cells) • autoimmune disease, viral infection, genetics • Stress response (“starving cells
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