This document discusses various psychological theories for why dieting often fails, including restraint theory, boundary theory, and ironic processes of mental control. Restraint theory proposes that dieting restricts eating to an unsustainable level, leading to disinhibition and overeating. Boundary theory extends this by suggesting breaking dietary rules can trigger overeating. Ironic processes theory suggests suppressing forbidden thoughts about food paradoxically increases their occurrence. The document also reviews research supporting these theories and factors that can increase dieting success, such as understanding obesity's causes, motivation, and behavior modification.

1. Psychology and Dieting
Peter Kilcoyne

2. 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

3. Video
• Psychology of Weight
Loss
• Discussion : What are
the key messages from
this talk?

4. Practical Exercise
• Investigate differences between males and females in
awareness and usage of diets
McCreary and Sasse 2007 young women more likely
that young men to be dieting to loose weight.
• Hypotheses
1) Females will be more likely to have been on a diet in
the last 12 months
2) 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

5. Analysis of Results
• Hypothesis 1
Females will be able to name more weight loss diets
than males
Independent t test
• Hypothesis 2
Females will be able to name more weight loss diets
than males
Chi Square

6. Theorys on Dieting
• Restraint Theory
• Boundary Theory
• Theory of ironic
processors of Mental
Control

7. Restraint Theory
Herman 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).

8. Boundary Model
Herman 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.

9. 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

10. 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

11. 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.

12. 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.

13. 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.

14. 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

15. 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

16. 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

17. 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

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