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Chapitre 12 - Notes Livres.docx

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PSYC 200

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Chapitre 12 MotivationI The Hungry AnimalMotives to EatA The Biology of WeightPsychologist use to think that being overweightsign of emotional disturbance Later research showed that overweight people arent moreless emotionally disturbed than slim people Also found that heaviness is not always a result of overeating Many heavy people eat in large quantity but so do skinny peoplein a study where people ate a lot skinny people had a hard time gaining weight as it is for most heavy people to lose weight1 Genetic Influences on Weight and Body ShapeExplanat biological mechanism keeps your body weight at a genetically influenced set point the weight you stay at when youre not trying to gain or losecan vary about 10 in each direct If you go too highlow your body will produce the need to eatreduce eating to go back to the set point Everyone has a genetically programmed basal metabolism rate the rate at which the body burns calories for energy and a fixed number of fat cell stores fat for energy and can change in size Obese people have 2 the number of fat cells as normalweight adults and their fat cells are bigger Fat cells cant disappear when you lose weight they only get smallerA complex interact of metabolismfat cellshormones keeps people at the weight their bodies are designed to be When a heavy person diets their metabolism slows down to conserve energy and fat reserves When a thin person overeats metabolism speeds up burning energySetpoint theory predicts that the heritability of weight and body fat should be high and indeed it is In twin and adopt studies heritability estimates fall between 040070 Identical twin who were raise apart have the same body weight and shape as twins raise togetherwhen they gain weight its at the same place Genes also determines how much brown fat energyburning type of fat that seems important in regulating body weight and blood sugar a person had in addit to usual white fat It is lacking in obese people which may be one reason that fat people cant burn all the calories they consumeA team of researchers isolated a genetic variation of the gene that causes mouse to become obese The usual form of the gene obeseob causes fat cells to secrete a proteinleptin travels through the blood to the brains hypothalamus which is involved in the regulation of appetite When leptin is normal people eat just enough to maintain their weight When leptin is low the hypothalamus thinks the body lacks fat reserve and signals the individual to overeat Studies suggest that leptin plays is most role early in life by altering the brain chemistry that influences how much an animalperson eats More specifically leptin helps regulate body weight by strengthening neural circuits in the hypothalamus that reduce appetiteby weakening circuits that stimulate it During a critical period in infancy leptin influences the format of those neural connect and the set point is set Some researches speculate that because of this early neural plasticity overfeeding infants while the hypothalamus is developing may later produce childhood obesity Researchers have identifies a number of other genes that are linked to being overweight They have discovered a gene that modulates product of a protein that apparently converts excess calories into heat rather than fat Possess of this gene may be one reason why slim people stay slim even when they temporarily overeatThose findings as often raise the publics hope for a breakthrough drug that will help people lose weight easily and quickly But taking leptin when overweight doesnt produce much weight lossleptin is only one of the influences on body weight dozens of genesbody chemicals are involved in appetitemetabolism rateweight regulat Ex receptors in nosemouth that keep urging you to eat more receptors in your gut telling you to quit and leptinother chemicals telling you that you stored enough fat or not Also your brain will get high on sugary food even if your tongue cant taste themenjoy their texture Sweets increase pleasureinducing dopamine levels in the brain making you crave more rich food Some obese people may have underactive reward circuitry which leads them to overeat to boost their dopamine level
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