Bio Expla of Obesity

• What does the genetic explanation of obesity describe BMI to be

  The genetic explanation of obesity describe BMI to be inherited and passed through generations through DNA. Thus a high BMI (obesity) is passed on from parent to child making obesity genetic in nature
• Twin studies in genetic explanations of obesity

  Twin studies have suggested a high heritability of obesity. For example, Maes et al conducted a meta analysis involving 75,000 individuals and found a BMI CR of 74% - MZ twins and 32% - DZ twins
• Adoption studies in the genetic explanation of obesity

  Adoption studies have also found a genetic link. Stunkard et al found a strong relationship between the weight category of adopted individuals and their biological parents and no significant relationship with adoptive parents
• What is serotonin involved in and associated with as a neural explanation for obesity

  Serotonin is involved in the control of feeding and research into humans and animals found that obesity is associated with abnormally low levels of serotonin
• What do normal and abnormal levels of serotonin help do in the neural explanation for obesity

  Normal serotonin levels help regulate eating behaviour, allowing normal functioning of the ventromedial hypothalamus

  Abnormal serotonin levels lead to the inaccurate satiety signals and thus disinhibited eating
• What does low serotonin lead to in the neural explanation for obesity

  Low serotonin also leads to more consumption of calories which leads to weight gain and can lead to obesity
• What is dopamine activity associated with in the neural explanation for obesity

  Dopamine activity is associated to the pleasure we derive from eating and cues related to eating (smell of food)
• What do dysfunctions in the dopamine system lead to + research

  • Dysfunctions in the dopamine system lead to obesity.
  • Wang et al found that obese individuals have fewer dopamine D2 receptors than people in the normal weight group
• What do fewer D2 receptors mean for dopamine activity

  Fewer receptors mean less dopamine activity therefore dopamine cannot perform the pleasure function when eating so the person doesn't feel as good after eating.
• What do obese people do in order to feel pleasure - what does this lead to

  In order to feel pleasure they overeat to trigger an increase in dopamine activity as an attempt to activate the reward. This leads to more consumption of calories which leads to weight gain which can lead to obesity
• Evals for the genetic explanation of obesity

  • W - Genetic - expression of genetic influence varies with age
  • W - genetic - evidence it relies on has questionable validity (Twin studies)
• Evals for the neural explanation of obesity

  • S - Neural - support for the role of serotonin
  • W - Neural - evidence it relies on is correlational (C+E)
• W- genetic - evidence it relies on has Q V. Twin studies assume the higher BMI CR for in MZ twins (100%) compared to DZ twins (50%) is bc they share more genes. Overlooks the possibility that the real reason behind higher CR is bc MZ twins are treated the same (e.g. given the same portion size) due to looking the same. The studies make the "equal environments assumption" where they assume that the environment that MZ and DZ twins share are equal in influence, when in reality, the environment that MZ twins have influenced them greatly. V of twin studies is Q - genetic explanation decreases in V
• W - neural explanation - evidence it relies on is correlational. Explanation argues low serotonin levels cause obesity. We don't know if low serotonin levels cause obesity or if low serotonin levels is a symptom of obesity. If former is true = explanation is validated. If latter is true - cause for obesity is in another explanation. For example, ppl may develop obesity not due to NT imbalances but instead due to observation and imitation of RMs who consistently overeat. As the evidence it relies on decrease in validity so does the theory
• S - neural expl - support for Serotonin. Ohia et al demonstrated the role of serotonin within obesity. This is especially true for serotonin receptors such as the 2C receptors. Abnormalities in these receptor sites in mice are associated with the development of late onset obesity. S bc it shows that dysfunctions in the serotonin system in mice does in fact lead to obesity. It's plausible to assume that dysfunctional serotonin systems in humans will lead to obesity. Increases V
• W - genetic - the expression of genetic influence varies with age. Research suggests that the genetic contribution to BMI is not stable across a person's lifetime. A meta-analysis of 88 studies by Elks et al found that heritability estimates of BMI varied according to the age group of individuals studied. They found the heritability figure of BMI was highest during childhood and then decreased during adulthood. W bc ...
• (W - genetic - influence varies with age)... W bc it shows that there's greater influence of genes on BMI but this diminishes as we age. Shows that the genetic influence on BMI isn't as dominant as the explanation proposes. This is because adults engage in practices like dieting which mediate genetic influences on BMI. Decreases validity