Presentation on theme: "Professor Glenn Wilson, Gresham College, London FEAST OR FAMINE? THE PSYCHOLOGY OF EATING."— Presentation transcript:
Professor Glenn Wilson, Gresham College, London FEAST OR FAMINE? THE PSYCHOLOGY OF EATING
TOO LITTLE, TOO MUCH Eating is a major problem. In the Developing World many people die because they don’t have enough food. In the West, people die more often because they are surrounded by too much. Either they overeat and become susceptible to obesity- related diseases or they starve themselves by compulsive fasting in the midst of plenty. Anorexia is a disease of the affluent middle- classes, not the poor. Around 10% of teenage girls in the UK have some kind of eating disorder and there has been a 13% increase over the last decade (Micali et al, 2013).
WEIGHT STEREOTYPES Popular belief that people are responsible for their own body shape. Negative traits are commonly ascribed to overweight people which “explain” and blame them for their condition (e.g. lazy, undisciplined). Some negative stereotypes also attach to slim people (e.g. vain, bitchy, mean). Yon Cassius has a lean and hungry look. He thinks too much - such men are dangerous. (Julius Caesar). Survey of 1800 women aged 18-40 (Glamour, 2012)
GENETIC INFLUENCE Body weight depends on interplay among many genetic and environmental forces. Twin studies show 40-70% heritability (Herrera et al, 2011). Many genes involved: 40+ locations so far implicated in various appetite, energy storage and metabolism processes. The best-known “obesity-risk” gene (FTO) is associated with a failure of satiation after eating (Karra et al, 2013). Epigenetics (gene expression effects without DNA alteration) also have impact. All of this makes control of weight very difficult. Though often thought of as “faulty” the survival advantage of obesity genes in lean times is obvious.
EATING HABITS Eating, drinking and exercise styles relate to obesity in complex ways. In a study of 1356 UK adults (Wilson 1985), body weight was associated with lack of exercise, overall food intake and eating in response to emotional stress. The latter seemed to reflect difficulty in maintaining dietary restraint in constitutionally heavy people. Diets tend to collapse at times when people are lonely, stressed or frustrated. Sugar consumption and daily drinking were unrelated to body weight or health problems; healthy people perhaps allow themselves more luxuries.
COMFORT EATING When a sports team loses, their fans eat more junk food the next day. Consumption of high calorie food increases on Monday in a city whose NFL team has lost on Sunday, whereas it decreases in the victors’ city (Cornil & Chandon, 2013). Effect is greater in cities with the most committed fans, when opponents are equally matched and defeats narrow. Similar findings with French soccer fans. A self-affirmation procedure (ranking and discussing core values) showed promise in countering the effect of a sports loss.
PERSONALITY AND BMI Impulsivity is the strongest personality correlate of weight gain. People get gradually heavier with age but those in top 10% for impulsivity averaged 24lbs more than those in the bottom 10%. Extravert people were also heavier; Conscientious and Agreeable people tended to be thinner. Those high in novelty-seeking were less successful in a weight management programme (Cloninger et al 2007). Diet and exercise require commitment and restraint, which are lacking in certain individuals. Longitudinal study of 1,988 adults in Baltimore (Sutin et al 2011).
HUNGRY SHOPPERS People who shop in a supermarket when hungry don’t buy more food but do buy more high-calorie products (Wansink & Tal, 2013). Subjects food-deprived for 5 hrs chose 5.72 high calorie products, vs 3.95 for sated controls. Interpreted as an effect of food insecurity. Suggested that weight- watchers should have a snack before shopping or go after lunch. Good to take a list (ideally not children).
THINKING YOURSELF FULL It is possible to trick people into feeling less hungry. Brunstrom et al (2012) used a soup bowl that would covertly refill or lower its quantity as people ate from it. Immediately afterwards, self-reported hunger was based on how much they had actually consumed. However, after 2/3 hours “hunger” went with how much they thought they had consumed (memory of bowl size). Food labels emphasising “light” and “diet” ingredients may be counterproductive, making us think we are less satisfied (so we eat more later). People shown a large quantity of fruit that has supposedly gone into their smoothie feel more “full” afterwards (Brunstrom 2012).
TV MAKES YOU FAT Watching TV contributes to obesity in several ways. Viewers are sedentary for long periods. If they snack while watching they lose track of how much they have had and consume more later (Mittal et al, 2011). If the content of the TV programme is food- related or depressing they will eat even more of any food that is handy (Laran, 2013).
SLEEP DEPRIVATION Late bedtimes allow more waking time for eating and late-night snacks tend to be more fattening (Spaeth et al 2013). Also, sleep loss is apparently stressful. Decreased activity in cortical evaluation regions of the brain (frontal and insular cortex) together with increased amygdala activity prompts desire for high-calorie, fattening foods (Greer et al 2013).
SOCIAL INFLUENCES People eat more in company than when alone. The social facilitation effect is stronger for friends/family than with strangers. Several reasons: (1) Eating is a shared activity that consolidates social ties. (2) Meal lasts longer, giving more time to eat. (3) Conversation is distracting, so self-monitoring is impaired (c.f. TV viewing). Eating with friends: +18% calories, Viewing TV: +14% (Hetherington et al 2006). People dining in twos tend to match their intake. Women eating with men eat more daintily than by themselves or with other women. Women eat less when men are present than with other women. Men not affected by company. (Young et al 2009).
OBESITY CONTAGION Social network analysis (Christakis & Fowler, 2010) indicates that obesity spreads like a virus. Friends have similar body build – neighbours do not. Norms for acceptable body build, portion size, etc. may be passed among friends to influence weight.
PRIMING INDULGENCE Seeing overweight people can lead us to eat more (Campbell & Mohr, 2011). People walking through a lobby answered survey questions that included a picture of either an overweight or normal-weight person. Afterwards they helped themselves to a bowl of wrapped sweets as a “thank you”. Those who saw the larger model took more sweets than the one who saw the thinner image (means of 2.2 vs 1.4). Four other studies confirmed this anchoring (reassurance?) effect. Sticking overweight images on the fridge door may have a reverse effect, shifting the idea of what is normal.
CONTROL STRATEGIES Many behavioural tips for controlling food purchase and consumption have been offered: (1) Don’t buy jumbo packs, multi-buy offers, snacks/sweets, meal-deals. (2) Store tempting foods well-packaged & out of sight/reach (not in office drawer or glove box of car). (3) Keep a healthy option to hand (fruit or unsalted nuts). (4) Drink water rather than fizzy and sugary drinks. (5) Decide serving size in advance. (6) Take your time when eating. (7) Don’t eat while doing other things Frequent use of such strategies discriminates normal from overweight people but not overweight from obese (Poelman et al, 2013).
SELF-MONITORING A key element in behavioural weight management programmes is some form of recording of eating patterns, weight or exercise (e.g., weighing self first thing every morning, or regular waist measurement). Paper diaries, websites and phone aps can be helpful. Does not seem to matter exactly what is monitored provided it is done on a regular basis (Burke et al, 2011). Motivational, and may detect patterns, giving early warning.
SLIMMING GROUPS Slimming classes like Weight Watchers are more successful than individual weight-loss programmes set up by doctors (Pinto et al, 2013). These are behaviourally oriented: focus on changing eating habits and promoting exercise. Usually led by trained peer counsellors who have achieved their own weight loss. Social context contributes to motivation and makes the treatment affordable.
ANOREXIA Pathological dieting, combined with denial of any problem. Most common in young women aged 12-19 (10x F/M). Become fearful of fat, obsessed by food/calories, develop rituals around eating/mealtimes and avoid food deceitfully (e.g., pushing food around plate and hiding it in napkin). Some follow pro-anorexia websites and smoke/take drugs rather than eat. May be maintained by endorphin highs evoked by starvation (Brindisi & Rigaud, 2011). Can be life-threatening; highest mortality of any mental illness (5-10% for every decade untreated). However, most (50-70%) get better within 2ys..
BODY IMAGE DISTORTION Anorexics overestimate their size. See themselves as fat (or claim to so as to justify food-avoidance?) Asked to adjust a mirror until the reflection is accurate they make themselves fatter than they really are. May turn sideways to go through a doorway they would comfortably fit head-on. Misperception applies specifically to themselves, not to others around them (Guardia et al, 2012). If not thinking themselves fat, may be proud of their bony form, believing themselves to be attractive.
RETREAT FROM PUBERTY Anorexia is strongly associated with onset of puberty (which gets earlier). Trigger may be observation of bodily changes like breast & hip enlargement, which arouse fear they are getting fat. A more psychoanalytic idea is that anorexia is specifically focused on avoidance of menstruation and a fear of growing up and assuming adult responsibilities. Carbohydrate intake seems geared to keep weight just below the level where cycle would commence. Recovering anorexics who regain normal luteinising hormone responses to LHRF show greater adolescent conflict on a repertory grid measure (Miles & Wright, 2011).
PERSONALITY AND ANOREXIA A particular set of personality traits is associated with anorexia (introversion, anxiety, perfectionism, OCD). Often pride themselves in self-control. A connection with autistic spectrum disorders has been suggested (“female Asperger’s”). Some of these associations diminish with recovery, so may be a result of the starvation effects on the brain rather than pre-existing causes of the disorder (Cassin & von Ranson (2005).
THE ANOREXIC BRAIN When people look at body images, input is via the medial occipital area (mOC), then the fusiform body area (FBA) to the extrastriate body area (EBA). Suchan et al (2013) found a lower density of neurons in the EBA in anorexic patients and reduced input from FBA. This weakened connectivity between FBA and EBA might account for the development of anorexia, or could be a result of it. Other studies have shown increased activity in emotional brain centres in response to food and body stimuli relative to controls (Zhu et al, 2012).
SPRING BIRTH Anorexia is more common in those born March to June (Northern Hemisphere). A similar relationship applies for major depression. Probably due to vitamin D deficiency in the mother during winter gestation. Allen et al (2013) found Australian mothers with low vitamin D (measured at 18 wks pregnant) were more likely to have teenage daughters with eating disorders. Data from meta-analysis of 4 UK cohorts, N= 1293 anorexics (Disanto et al 2011).
MANOREXIA Concern with muscularity may be a male equivalent of female anorexia. Field et at (2013) found 9.2% of male adolescents had high concerns re muscularity (only 2.5% concerned about thinness). Often leads to use of supplements (e.g. growth hormone, steroids) harmful to health. Those concerned with thinness more prone to depression than those with muscularity concerns. Body image problems in general more common in homosexual men.
BULIMIA Binge eating of high calorie food is followed by purging or self-induced vomiting. Stomach acids can damage throat, cause tooth decay & bad breath. Also more common in young women but weight likely to be normal (Princess Diana). Men not immune (John Prescott, Elton John). Whereas anorexia goes with anxiety and constraint, bulimia relates to impaired self-regulation and impulse control (Marsh et al, 2009). Comorbid with borderline personality disorder, substance abuse, shoplifting, self-mutilation and sexual disinhibition.
TREATMENT May be necessary at first to hospitalise and force-feed. CBT (modification of beliefs & attitudes) is favoured treatment but co-operation not always forthcoming. Important to look at motivation and ensure readiness to change. May need to treat co-occurring problems such as anxiety, perfectionism, depression, substance abuse and attention deficit. Drugs (e.g. SSRIs) may help, especially if depression is involved. Some experimental work with deep brain stimulation, but this is a last resort. The Maudsley Model (Le Grange, 2005) involves the family in treatment, e.g., teaching parents how to supervise meals. However, family attitudes are sometimes part of the problem.
FAD DIETS Diet plans are a major industry. Usually work by excluding certain types of food, thus reducing total calories if maintained long-term (Pagoto & Appelhans, 2013). Intermittent fasting also limits calorie intake, unless there is “catch-up”. Compliance is poor because hunger increases and body goes into distress mode (release of stress hormones and lowered metabolism). When the diet stops there is rapid rebound to baseline or beyond. Mostly unhealthy compared with balanced diets and exercise. Breatharianism (living only on nutrients of sun and air) is most effective but eventually fatal.
SKINNY MODELS Models in women’s magazines are often airbrushed and unrealistic. Catwalk models are pressured to be dangerously thin so as not to distract from the clothes. Proliferation of unhealthily thin models in the media has been linked to body dissatisfaction, substance abuse (smoking/heroin), eating disorders and depression (Grabe et al, 2008). However, only women high in neuroticism suffer harmful effects of thin models (Roberts & Good, 2010). Long exposure to thin-ideals can sometimes increase body satisfaction by prompting dieting and exercise (Knoblock-Westerwick & Crane, 2012). If Barbie were real she would have a 16in waist and be infertile.