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Lecture 3

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PSYC 2230
Pauline Charlton

Lecture 3 • The Biological Basis of Weight Regulation • The Search for Hunger/Satiety Signals – Feelings of hunger rise and fall with levels of glucose and insulin – Possible link to the number of fat cells in the body • Lateral Hypothalamus (LH) – Stimulation leads to hunger – Lesioning leads to self-starvation • Ventromedial Hypothalamus (VMH) – VMH lesioning leads to hunger – VMH stimulation causes an animal to stop eating • Short-Term Appetite Regulation • Pancreas hormone insulin helps convert glucose into fat • When glucose levels fall, insulin productions increases and we feel hungry • Cholecystokinin (CCK) — satiety hormone produced by the intestine • Ghrelin — appetite stimulant produced by stomach • The Glycemic Index of Some Common Foods • Unhealthy breakfast trends • “Dessert for breakfast” • “Super-sizing” • Calorie — amount of energy needed to raise the temperature of 1 g of water 1 degree Celsius • Long-Term Weight Regulation • Laboratory mice with a defective gene for regulating the hormone leptin become obese • Leptin levels increase with body fat • Neurons in the arcuate nucleus (ARC) of the hypothalamus contain many receptors for leptin • Cholesterol and Disease • Framingham Study – Best predictor of heart disease is the amount of “bad cholesterol” (LDL) in the body • Serum cholesterol is determined partly by heredity • Diet (especially saturated fat) is implicated in one-third of all cancer deaths in the United States • BMI • Male Pattern Obesity — “apple-shaped” body with excess weight around upper body/abdomen • Female Pattern Obesity — “pear-shaped” body with excess weight on thighs/hips • Basal Metabolic Rate and Caloric Intake • Basal Metabolic Rate (BMR) – Body’s base rate of energy expenditure – Influenced by heredity, age (higher in younger people), activity level, and body composition (fat tissue has a lower metabolic rate) • Set-Point Hypothesis – The point at which an individual’s “weight thermostat” is supposedly set – When the body falls below this weight, an increase in hunger and a lowered metabolic rate may act to restore the lost weight – Set- or settling-point • Diet and Disease • Body expends only 3 calories to turn 100 calories of fat in food into body fat • Body expends 25 calories to turn 100 calories of carbohydrate into body fat • Humans have a natural craving for fat (a legacy from our evolutionary past when food was not plentiful?) • Typical Western diet: 40%–45% of total calories are from fats • Poor diet (especially saturated fat) is implicated in one-third of all cancer deaths in the United States • The B
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