Psychological Explanations for Obesity (AQA A Level Psychology): Revision Note

Restraint theory

• Herman & Polivy (1975) developed restraint theory, a cognitive theory of obesity arguing that restrained eating is counterproductive and ultimately self-defeating, as a significant proportion of restrained eaters overeat to the extent that they become obese

• Limiting food intake leads to psychological stress, lowered mood and cravings

• Restraint theory combines two factors:

  • Cognitive control – restrained eaters categorise foods as 'good' or 'bad' and create rules and beliefs about which foods are allowed and which are forbidden, replacing physiological control with conscious control

  • Paradoxical outcome – the restrained eater becomes more preoccupied with food, actively ignoring physiological signals of hunger and satiety, which leads to disinhibition of eating behaviour

Disinhibition

• After a period of restraint, individuals become tired of restricting themselves and start eating as much as they want, often taking an 'all or nothing' approach

• Restrained eaters are vulnerable to internal cues (such as lowered mood) and external food-related cues (such as media images), known as disinhibitors, which lead to a loss of control over restrained eating

  • Once disinhibited, the individual may reason that as they have already broken their rules there is no point in stopping, which Herman & Polivy call the 'what the hell effect', marked by passivity and resignation

    • This disinhibition sometimes leads to binge eating

• After a period of disinhibition, some individuals will go back to restraint in what becomes a cycle of dieting and bingeing (also known as ‘yo-yo dieting’), while others continue to overeat, leading to obesity

The boundary model

• Herman & Polivy (1984) developed the boundary model, in which food intake lies on a continuum from an aversive state of hunger at one end to an aversive state of satiety at the other

• Different physiological processes determine how much and when we eat on each end of this continuum, with low energy leading to hunger and a feeling of fullness leading to satiety

• Between these boundaries lies a zone of biological indifference, where eating is under cognitive and social control rather than physiological control

  • The unrestrained eater will eat until they reach satiety, while the restrained eater will eat until they reach their cognitive boundary, which is determined by the limit they have set for themselves

  • Restrained eaters have a lower hunger boundary, so are less responsive to feelings of hunger, and a higher satiety boundary, so they need more food before they consider themselves full, meaning their zone of biological indifference is wider and they are more vulnerable to disinhibition

• The boundary model demonstrates how, once restraint is replaced by disinhibition, previous dieters eat more than those who are not controlling their food intake psychologically and obesity is the result

Research which investigates psychological explanations for obesity 

• Herman & Mack (1975) used a questionnaire to identify participants’ level of restrained eating and then gave them ice cream in a mock ‘taste test’

  • They found that restrained eaters ate significantly more ice cream than a control group of unrestrained eaters if they had been given a milkshake to drink before the study

    • This suggests they had already exceeded their cognitive boundary in drinking the milkshake, supporting restraint theory and the boundary model

• Adriaanse et al. (2011) found that when female students who were trying to cut down on their intake of unhealthy snacks were presented with diet intentions expressed in a negative form (e.g., ‘When I am sad, I will not eat chocolate’), they ate unhealthy snacks more often in the following week, consuming more calories than a control group, which supports the restraint theory

Evaluation of  psychological explanations for obesity 

Strengths

• Wardle & Beales (1988) randomly allocated 27 women to a restrained-eating diet group, an exercise group or a control group, and found that after seven weeks the restrained eaters consumed the most calories overall, experiencing occasional disinhibition of their eating when they would binge beyond feeling full

  • This supports the argument that restraint is a causal factor in overeating, rather than simply co-occurring with it

• Psychological explanations for obesity have been used to successfully develop cognitive behavioural therapy for binge-eating and obesity (Mesarič et al, 2023)

Limitations

• Savage et al. (2009) measured dietary restraint and disinhibition in 163 women at the start of a study and every two years afterwards over a six-year period, and found that increases in restrained eating were linked to decreases in weight

  • This suggests that restrained eating leads to weight loss rather than weight gain, at least in the short term, the opposite of what restraint theory predicts

• Much of the data comes from self-report questionnaires and daily eating diaries, which are subject to a social desirability bias, which would lower the validity of the findings

Issues & Debates

• The theory reduces obesity to cognitive processes like restraint and disinhibition, overlooking complex interactions with biological and social factors (e.g., genetics, economic access to food, cultural eating norms)

  • This oversimplifies the causes of obesity, limiting the theory’s explanatory power

• Psychological explanations of obesity are nomothetic because they aim to establish general laws of behaviour by identifying patterns and mechanisms that apply across individuals

  • This allows for large-scale treatments like CBT to be developed but may overlook individual differences in experiences of food restriction and emotional triggers