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Problems with Set-Point Theories

Problems with Set-Point Theories. Variability of body weight Set points and health Free-feeding does not lead to optimum health Positive effects seen with caloric-restriction. More Problems…. Altering metabolism Diet-induced thermogenesis – increases in body fat increase body temperature.

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Problems with Set-Point Theories

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  1. Problems with Set-Point Theories • Variability of body weight • Set points and health • Free-feeding does not lead to optimum health • Positive effects seen with caloric-restriction

  2. More Problems… • Altering metabolism • Diet-induced thermogenesis – increases in body fat increase body temperature

  3. Why do we care? • Can control our body weight • Then why is there an obesity epidemic?

  4. Why Is There an Epidemic of Obesity? • Evolution favored preferring high calorie food, eating to capacity, storing fat, & using energy efficiently • Cultural practices and beliefs promote consumption

  5. Mutant Obese Mice and Leptin • Mice are 3X normal weight • Lack leptin, a hormone produced by fat cells • Leptin – a negative feedback fat signal

  6. Insulin: Another Negative Feedback Signal • Like leptin, • levels correlated with body fat • receptors found in the brain • reduces eating at levels too low to be aversive or to affect blood glucose • Insulin deficiency leads to hyperphagia, but not obesity – food not converted to fat in the absence of insulin

  7. Drastic Measures • Wiring jaw shut • Stapling stomach • Gastric Bypass Surgery

  8. Anorexia nervosa • A disorder of under consumption of food • Weighs 85% or less • Affects puberty, menstruation, sex drive • Associated with depression, irritability, withdrawal and peculiar behaviors

  9. What causes Anorexia? • No single known cause • Culture • Families • Life changes or stressful events • Personality traits • Biology

  10. More on biology and psychology • Serotonin (high and low) • Autoimmune response to melanocortin peptides • “Perceive” themselves as larger • Lack overconfidence bias • Poor cognitive flexibility, attentional biases

  11. Anorexics are ambivalent about food • Cephalic-phase response • Preoccupied with food • Disgusted by sweet and fatty tastes • Feel ill after a meal

  12. Anorexia and Positive Incentives • Decline in the positive-incentive value of eating food vs. interacting with food • Starvation normally triggers a radical increase in the positive-incentive value of food

  13. Meals • Taste aversions that reduce the motivation to eat

  14. Bulimia Nervosa • A psychological condition in which the subject engages in recurrent binge eating followed by an intentional purging (i.e. vomiting, laxatives, diuretics, excessive exercise, etc.)

  15. Causes and Factors • Lack of control • Caucasian groups • Women: 90% • Activities that emphasize body type • Anxiety and other mood disorders

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