Psychological Explanations for Obesity

• Restraint theory:

  • Herman and Polivy (1975) developed a cognitive theory of obesity – restraint theory
  • Attempting to lose weight usually involves restrained eating: deliberately limiting the amount of food you eat
  • Herman and Polivy argue that restrained eating is counterproductive and self-defeating
  • They noticed that most people who restrain their eating fail to lose any weight 
  • Some even overeat to the extent that they become obese
• Restraint theory:cognitive control

  • Restrained eaters set strict limits on their food intake
  • They categorise food as ‘good’ or ‘bad’ and create rules/beliefs about which foods they can eat
  • A restrained diet is a highly organised way of imposing control which restrained eaters believe will allow them to lose weight
  • This control is cognitive because the individual has to consciously think about their weight and eating a lot of the time
• Restraint theory: paradoxical outcome

  • However, the result if the restrained eater becomes more preoccupied with food rather than less
  • By placing limits on what and how much they eat, the restrained eater no longer eats when they are hungry and stops when they are full
  • Their eating is no longer under physiological control
  • They now actively ignore physiological indicators that signal hunger and satiety (feeling full)
  • This means that they don’t eat when they should and they do eat when they don’t need to
• Disinhibition:

  • Obesity is not solely caused by restraint, but rather a cycle of restraint and disinhibition.
  • Restrained eaters are vulnerable to cues like smells or media images, leading to a loss of control over their eating habits.
  • This can result in disinhibited eating, or binges, which is triggered by all-or-nothing thinking. If a single cue triggers disinhibited eating, the individual continues to eat as much as they want.
• boundary model:

  • Herman and Polivy (1984) explained the impact of restrained eating and disinhibition in their boundary model of obesity
  • Food intake exists on a continuum from hungry to satiated (feeling full)
  • Biological processes determine this (e.g. Glucose levels too low so need to eat, or too high so need to stop)
• boundary model:

  • Eating begins at the hungry boundary and stops at the satiety boundary
  • Between these two points is the ‘zone of biological indifference’ where biological processes have little effect
  • Instead cognitive and social factors have their greatest influence on food intake, when we are neither particularly hungry nor particularly full
• boundary model:

  • Restrained eaters have a lower hunger boundary, so they are less sensitive to feeling hungry
  • However, they also have a higher satiety boundary, so they need to eat more to feel full
  • For restrained eaters, the zone of biological indifference is wider
  • This means more of their eating behaviour comes under cognitive rather than biological control
  • This makes them vulnerable to the effects of disinhibited eating
  • Restrained eaters have a self-imposed diet boundary
• boundary model : - restrained eaters

  • This diet boundary is some distance below the satiety (feeling full) boundary set by biological processes
  • When restrained eaters break this diet boundary (e.g. eat more than 2 squares of chocolate) they carry on eating beyond the satiety boundary
  • This is an example of disinhibition which Herman and Polivy call the ‘what the hell’ effect 
• Boundary model:

  
• AO3:

  • A strength of restraint theory is that there is research to support the link between restrained eating and overeating
  • Wardle and Beales (1988) randomly allocated 27 obese women to 3 conditions: restrained eating, exercise and control group. They assessed their eating for 7 weeks.
  • When participants’ eating was assessed in the fourth and sixth week, the restrained eaters had eaten significantly more than the other participants
• AO3 continued

  • This supports the theory that restraint causes overeating, because it suggests that although the restrained eaters generally tended to eat less than the other groups throughout the week, they experienced occasional disinhibition when they would binge eat.
• AO3:

  • strength of boundary model - can lead new treatments for obesity
  • as it suggests that dietary restraint can lead to disinhibition and overeating, ultimately causing obesity. Zandian et al. (2009) recommend that weight loss advice should focus on training dieters to eat more slowly, ensuring that treatments for obesity do not maintain or worsen the disorder.
• AO3:

  • There is support for the idea that restrained eaters are vulnerable to external cues, leading to disinhibited eating
  • Boyce and Kuijer (2014) found that restrained eaters responded to media images of thinness by eating more in a ‘taste test’ than unrestrained eaters
  • This suggests that these images are disinhibitors which trigger eating in restrained eaters. This can then lead to obesity, as predicted by the restraint theory.
• AO3:

  • limitation of the restraint theory is that not all research supports its key principle
  • Savage et al. (2009) measured dietary restraint and disinhibition in 163 women at the start of the study and then every two years over a six year period. 
  • They also measured changes in their weight 
  • They found that increases in restrained eating were linked to decreases in weight (significant negative correlation)
  • This is a limitation of restraint theory as it suggests that restrained eating while dieting leads to weight loss rather than weight gain