13.4.2 Psychological Explanations for Obesity

• Restraint theory suggests that deliberately limiting the amount of food eaten leads to the surprising outcome of actually eating more, because of preoccupation with food, and this leads to obesity 
• Limiting food intake leads to psychological stress, lowered mood and cravings
• Restraint theory combines two factors:
  • Cognitive control - restrained eaters set strict limits on what they may and may not eat and how much, forcing control in a highly organised manner
  • Paradoxical outcome - preoccupation with food means the individual does not eat when their body signals hunger and eventually when they do eat they do not stop when their body sends signals that they are full, with obesity as the result

• 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
• Disinhibition starts by being influenced by food cues that are internal (e.g. lowered mood) and external (e.g. cooking smells or images of food)
  • Once the individual starts disinhibited eating, they may feel that they are a failure and decide that they might as well eat everything (a sort of sunk-cost fallacy)
  • 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

A period of disinhibition can result in binge-eating.

• The boundary model explains how food intake lies on a continuum ranging from feeling hungry to feeling full (satiety) 
• 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 the area where eating behaviour is under psychological control, and not subject to either physical hunger or satiety
• 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 themselves
• Dieters have a large range between their hunger and satiety levels because it takes longer for them to feel hungry, but physically they need more food to reach satiety
• 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

The boundary model of obesity.

Research which investigates psychological explanations for obesity 

• Herman and Mack (1975) used a questionnaire to identify participants’ level of restrained eating and then gave them ice cream in a mock ‘taste test’, finding 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, as they had already gone beyond their ‘diet boundary’ in drinking the milkshake, supporting restraint theory and the boundary model 
• Adriaanse (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

• Disinhibition is a strong argument for weight gain leading to obesity in cultures where there is a high daily number of overeating opportunities from fast food outlets, such as burger stalls and pizza restaurants
• Psychological explanations for obesity have been used to successfully develop cognitive behavioural therapy for binge-eating and obesity (Mesarič et al, 2023)

Weaknesses

• Restraint theory cannot explain those who succeed in attaining weight loss through restrained eating or how individuals with anorexia nervosa experience huge weight losses through restraint
• 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

Link to Approaches: 

Psychological explanations for obesity take a cognitive approach as they are focusing mainly on the internal mental processes of restraint and disinhibition, such as lowered mood and feelings of failure.

However, the boundary model is a good example of combining biological and cognitive factors to explain eating behaviour and obesity, as the model explains the relationship between the physical boundaries of hunger and satiety and cognitive control of eating.