Eating Behaviour

1. Eating Behaviour

2. This session focuses on what affects our eating behaviour: culture, mood, health, and diet. Biological explanations are considered as well as eating disorders

3. Eating Behaviour

4. 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

5. 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

6. 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

7. 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

8. Biological Explanations of Eating Behaviour

9. 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)

10. Control of eating behaviour.

11. 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

12. 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

13. Eating Disorders

14. 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

15. 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

16. Anorexia vs. Bulimia • 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 • 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 self-focused, concerned with control

17. 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

18. 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

19. Psychological Explanations Psychodynamic model Causes: • Repressed fears • Unconscious desire to remain a child • Lack of identity/enmeshed family • Ineffective parenting

20. 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

21. 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

22. 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

23. 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

24. Psychodynamic Explanations • Food is a symbol for love • Oral fixation of sufferers • Preferred foods resemble breast milk, i.e. sweet and creamy • Untestable

25. Learning Theory Explanations Causes: • Maladaptive learning • Conditioning and social learning • Energy-dense foods given as rewards • Affluence and over-eating • Obese role models

26. 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

27. 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)