Transcript Eating Behaviour

Eating Behaviour
1
• This session focuses on what affects our
eating behaviour: culture, mood, health,
and diet. Biological explanations are
considered as well as eating disorders
2
Eating Behaviour
3
Culture
• Social Norms
– What is acceptable socially as food?
• Religious norms
– Hindu and Jewish rules
• Learning
– Parents and family; peers; social learning,
conditioning
• Schemas
– Cultural norms
4
Mood
• Low mood
– Carbohydrate cravings
– Conditioning, social learning,
serotonin, or endorphin rush?
• Chocolate
– Psychotropic effect? (Parker et al., 2006)
– Sensory pleasure
– Social learning or conditioning (Macht
& Dettmer, 2006)
• Caffeine
– Increased positive mood (Smith et al., 2003)
– Noradrenaline and cognition
• Serotonin and noradrenaline
– Low levels and low mood
– Affects tastiness of food and hence amount eaten
5
Health Concerns
Healthy diet, food safety, food quality
• UK government survey
– Awareness of concerns a mismatch with eating
behaviour
– Obesity problem
• Cheap food
– Quality, availability, and advertising
• Fruits and organic/higher quality food
– Cost and availability
• Trust in official information
6
Dieting
Success or failure?
• 22% of UK adults are obese,
75% overweight
– Lopez-Jimenez (2008)
• Short-term success in dieting
to lose weight
– Environmental and biological
factors
• Psychological factors
• Exercise
7
Biological Explanations of Eating
Behaviour
8
Neural Mechanisms
Hunger, satiety, and the brain
• Hypothalamic eating control centres
– LH and VMH, cortex and amygdala (de Araujo et al., 2006)
• Insulin, leptin, and blood glucose level
–
–
–
–
–
Rosenzweig et al. (2002)
Lavin et al. (1996)
Horvath (2005
Licinio et al. (2004) and London (2007)
Ravussin et al. (1997) vs. Johnstone et al. (2006)
• PYY hormone
– Batterham et al. (2007)
9
Control of eating behaviour.
10
Evolutionary Explanations of Food
Preference
• Foods high in energy and nutrients aid survival
to reproduce
– Cross-cultural preference for protein, fats/oils, sugar
– Nutrient-dense and energy-dense
– Adaptive to be omnivorous
– Paleolithic diet (Eaton & Konner, 1985)
– AMY1 gene distribution
– Brain size
11
Alcohol
• Part of the human diet from the beginning
• Scent aids finding ripe fruit
– Dudley (2002)
• Reduces cardiovascular disease, increases
lifespan, source of energy
– Consumption adaptive
• Disinfectant nature
– Ridley (1999)
• Mu opiate brain receptors and endorphins
– Alcohol and pleasure
12
Eating Disorders
13
Anorexia Nervosa
Clinical characteristics:
• DSM-IV criteria
– Less than 85% expected body weight
– Intense fear of weight gain
– Maladaptive cognition about personal body weight
– If female, amenorrhoea
• 90% sufferers are female
• 0.5% frequency in the West
• Possible long-term serious physiological changes
14
Bulimia Nervosa
Clinical characteristics:
• DSM-IV criteria
– Numerous episodes of binge eating
– Frequent inappropriate compensatory behaviours,
e.g. purging
– Frequency of the above
– Maladaptive cognition about oneself
– Bingeing and purging outside anorexia episodes
• Significant increase in past 40 years in the West
• Possible long-term physical damage
15
Anorexia vs. Bulimia
• Often starts during
adolescence
• Often follows dieting
• Associated with anxieties and
depression
• Involves maladaptive thinking
• Still rare
• Serious weight loss, less than
85% of expected
• Not so sociable or concerned
with attractiveness, more selffocused, concerned with
control
• Often starts during
adolescence
• Often follows dieting
• Associated with anxieties and
depression
• Involves maladaptive thinking
• Becoming common
• No serious weight loss, within
10% of expected
• Sociable, concerned with
attractiveness, have mood
swings, impulsive
16
Biological Explanations
• Inherited maladaptive genes
– Family and twin studies
• Strober and Humphrey (1987), Holland et al.
(1988), Kendler et al. (1991)
– Environment and culture
• Loehlin and Nichols (1976), Comer (2001)
– Anorexia genes associated with perfectionism
• Bachner-Melman et al. (2007)
– Adoption studies
– Possible under-diagnosis in males
17
Neurochemicals
Serotonin and bulimia
• Low serotonin activity
– Carrasco et al. (2000)
• Serotonin gene predisposition
– Monteleone et al. (2007)
• Same serotonin transporter gene
– In different bulimic types (Wonderlich et al.,
2005)
• Diathesis–Stress model
18
Psychological Explanations
Psychodynamic model
Causes:
• Repressed fears
• Unconscious desire to remain a child
• Lack of identity/enmeshed family
• Ineffective parenting
19
Cognitive Model
Causes:
• Maladaptive cognitions, e.g. about body
shape and size, effects of food
• Perfectionism in mothers
• Low self-esteem of sufferers and mothers
20
Cultural Model
Causes:
• Disorders much more common in the
West
• Rare in traditional non-Western cultures
• Increase as Western culture introduced
• Body dissatisfaction is greater in the West
• Cultural pressures are greater in
adolescent girls
21
Evolutionary Theory
Causes:
• Eating disorder-type behaviour was
adaptive for our ancestors
• Bingeing when food was plentiful
• Over-expression of eating behaviour genes
• Anorexics would not drain food resources
• Anorexia could demonstrate acceptance of
defeat
22
Obesity
• Too much body fat
• Linked to cardiovascular disease,
hypertension, shorter lifespan
• Increased in UK in past 25 years
• UK frequency of over 20% both sexes
Causes:
• Over-eating, poor diet, lack of exercise,
maladaptive genes
23
Psychodynamic Explanations
• Food is a symbol for love
• Oral fixation of sufferers
• Preferred foods resemble breast milk, i.e.
sweet and creamy
• Untestable
24
Learning Theory Explanations
Causes:
• Maladaptive learning
• Conditioning and social learning
• Energy-dense foods given as rewards
• Affluence and over-eating
• Obese role models
25
Environmental/Lifestyle Explanations
• Obesity is a new disorder
Causes:
• General lack of exercise and calorie-rich
diets
• Children take little exercise
• Faulty estimations of food intake and
exercise
26
Genetic Explanations
• Family studies
– Stunkard et al. (1986)
• Ethnic group studies
– Caucasian, Afro-Caribbean, and Hispanic
• Twin and adoption studies
– Plomin et al. (1997), Mark (2006)
• Genetic variants identified
– Henderson (2008)
27