Psychological explanations of obesity

• Restraint Theory:

  • Suggests that the more restrained you are & the more you are trying to avoid over-eating, the more you actually eat, so you are therefore prone to obesity.
• Herman & Mack developed restraint theory & classified people either as rigid restrainers or flexible restrainers:

  • Rigid eater= all or nothing approach
  • Flexible eater= allows the odd treat in moderation
  • Restrained eater= if you are currently dieting
• The Boundary Model:

  • Hunger exists on a continuum between hunger & satiation, and the gap between the 2 is larger for someone prone to obesity (& therefore more likely to be restrained/ on a diet), as they are sensitive to feelings of hunger, but not to satiation.
  • This gap is known as the 'zone of biological indifference'- you are neither hungry or full, so eating behaviour is largely influenced by social & environmental factors.
• The Boundary Model:

  • When on a diet, restrained eaters stop when they reach a strict cognitive boundary set by themselves- means only eating a certain number of calories, so rather than eating until satiation, you eat what your restricted diet allows.
  • If a low calorie preload is given (fruit), dieter= still within their diet boundary, so will only eat up to the boundary after this.
  • If a high calorie preload is given (ice-cream), dieter= pushed beyond their boundary- therefore lose inhibitions & eat until/ beyond satiety ('what the hell affect'- may as well keep eating).
• Evidence for The Boundary Model:

  • Dieting makes you eat more- Herman et al, uses preload method.
  • 3 independent conditions with 15pps in each, group 1 had no preload, group 2 had milkshake preloads, group 3 had 2 milkshakes. All were given 3 tubs of different flavoured ice-cream & given 10 mins to rate them for taste- were told they could eat as much as they wanted. Were given a questionnaire to assess their normal dietary restraint.
• Results from Herman et al study using preload method:

  • Results: each group were divided into high (dieters) or low (non-dieters) restraint eaters. Low restraint ate less ice-cream when they had already had a milkshake preload- normal as they would already feel full from the milkshakes.
  • High restraint eaters ate significantly more ice-cream in the preload (milkshake) conditions than in the no preload condition.
  • This shows support for The Boundary Model.
• Evaluation of The Boundary Model- weakness:

  • Supporting evidence lacks ecological validity- was lab-based & in the real world, dieting violations would not lead to such extreme over-eating and that dieters can control their eating.
  • Researchers provide evidence for this by tracking food intake of dieters in their everyday lives & found that diet violations did not lead to overeating.
• Disinhibition- states people might overeat in response to a variety of stimuli & circumstances unrelated to how biologically hungry we feel.
• Bond et al identified 3 types of disinhibition:

  1. Habitual disinhibition- overeating in response to daily life circumstances, eg always having a glass of wine on a Friday night, regardless of thirst.
  2. Emotional disinhibition- overeating in response to emotional stress such as anxiety or depression, eg having a stressful day & thinking you deserve a whole tub of ice-cream.
  3. Situational disinhibition- overeating in response to specific environments/ situations, eg eating at a buffet at a party, having already eaten at home.
• Evaluation of Disinhibition- weakness:

  • Majority of research into this area has been conducted on white women, so it's hard to generalise the theory to males or other races. Research actually suggests cultural differences.
  • Atlas et al found that restraint & disinhibition was lower amongst African American students compared to white students.
  • A similar study by Bellise et al shared a lower score for men compared to women. This suggests that it's in fact white women who are most prone to disinhibition & that it's a more important factor for this group when it comes to weight gain than others