Psychology and Dieting

Peter Kilcoyne

Spec and Exam Question

• Explanations for the success and failure of dieting

• Discuss explanations for the success and/or failure of dieting. (4 marks + 16 marks) June 12

Video

• Psychology of Weight Loss

• Discussion : What are the key messages from this talk?

Practical Exercise

• Investigate differences between males and females in awareness and usage of dietsMcCreary and Sasse 2007 young women more likely that young men to be dieting to loose weight.

• Hypotheses1) Females will be more likely to have been on a diet in the

last 12 months2) Females will be able to name more weight loss diets than

males• Instructions each student ask one male and one female

subject to fill in diet survey

Analysis of Results

• Hypothesis 1Females will be able to name more weight loss diets than malesIndependent t test• Hypothesis 2Females will be able to name more weight loss diets than malesChi Square

Theorys on Dieting

• Restraint Theory• Boundary Theory• Theory of ironic

processors of Mental Control

Restraint TheoryHerman and Mack 1985

• Diets often fail because most people find it impossible to continue restrained eating

• Restraint followed by disinhibition “eating more as a result of loosening restraints in response to emotional distress, intoxication or preloading” (Herman and Polivy, 1988).

Boundary ModelHerman and Polivy 1983

• Extension of Restraint Theory taking cognitive factors into account

• e.g. If someone on a diet has a rule of boundaries. “I will not eat any biscuits” amd they break this rule they may then go onto overeat as a response to breaking their boundaries.

• Also physiological factors – body has body weight set point, when our weight is lowered homeostatic mechanism kick in to increase weight back to set point.

Herman and Mack (1975)

• Dieters and non Dieters given a high cal or low cal preload snack

• Then given a “taste test”• Dieters with high preload ate more than low

preload dieters• Non dieters with high preload are less than

low preload non dieters

Theory of ironic processors of Mental Control Wegner (1994)

• Attempted suppressing a thought makes you more likely to think about it.

• Dieters in trying to suppress thoughts about food think about it more

• Leads to over eating

Supporting Research

Keys et al (1950) studied 36 non-dieting conscientious objectors to the Korean War. They were given half their usual daily food intake for 12 weeks and lost 25% of their normal body weight. Keys et al reported that they became obsessed with food and started hoarding or stealing it. Many became depressed and couldn’t concentrate. When they were later allowed to eat freely, many ate continuously and became binge eaters. This suggests that the food restriction caused changes in the participant’s cognitive states so that the restricted food became an obsession.

Supporting Research

Wardle and Beales (1988) randomly assigned 27 obese women to either a diet group, an exercise group or a control group (no intervention) for 7 weeks. All participants took part in a laboratory procedure to assess their food intake at weeks 4 and 6. The results indicated that participants in the diet condition ate more than those in the exercise group and also those in the control group. This supports the idea that simply thinking about restricting food (as associated with the word ‘diet’) can cause overeating.

Supporting Research

Further support comes from Wegner et al (1987) who asked participants not to think of a white bear but to ring a bell if they did. They found that participants rang the bell more often than participants who were specifically asked to think about a white bear! The same processes occur with dieters as denial of certain foods makes a person more preoccupied with them; something that is forbidden becomes desired.

How effective is dieting?

• Wing and Phelan (2005) 20% of dieters maintain 10% weight loss over a year (80% don’t)

• Ayyad and Anderson (2000) looked at 17 longitudinal studies average of 15% of dieters maintained weight loss

Factors that increase the success of dieting

• Rodin et al (1977) importance of understanding the cause of obesity and individuals motivation for weight loss.

• Kiernan et al (1998) being dissatisfied with body shape and placing high value on attractiveness were important factors in successful weight loss.

• Ayyad and Anderson (2000) group therapy and behaviour modification improve success

Weight loss regainers vs Weight loss maintainers

Ogden and Hills(2008) Maintainers had• Belief in behavioural model of obesity (its

what I do not my glands or genetics)• Reduced choice over what and when they eat• New identity as healthy thinner person

Research Task

• Go to google scholar http://scholar.google.co.uk/

• Search for dieting or weight loss• Choose a research article that is relevant to

todays lesson• Summarise the research article in the “

glossary of research” on PKs Moodle course

Essay

Discuss explanations for the success and/or failure of dieting. (4 marks + 16 marks)