Eating Behaviour

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Psychology Revision Eating Behaviour

Transcript of Eating Behaviour

Eating Behaviour

Attitude towards food

Attitudes towards foody One way to understand how different factors affect eating is by y y y y

examining our attitudes towards eating and certain types of food. Attitudes are judgements and develop on the ABC model: Affect is the emotional response to the stimulus eg, not liking the taste. Behaviour is the verbal or behavioural reaction. Cognitive response is the evaluation of the object.

y Example

An individual eats some bacon. A. They dislike the bacon. B. They spit it out. C. They decide that they don t like that brand of bacon and therefore will not try it again.

Theory of Reasoned Actiony This theory was made by Ajzen and Fishbein(1980). y It is a social-cognition model that states that

intentions are the best way to predict actions.y Two factors influence intentions, and these are: 1. Attitude towards behaviour 2. Perceived social pressure

Theory of Reasoned ActionBeliefs about the outcome of the behaviour. Eg, if I stop eating junk food I will be healthier Evaluations of outcome. Eg I want to be healthierNormative Beliefs about the behaviour. Eg my friends think I should stop eating junk food Motivation to comply Eg I want to be liked by my friends, so I ll do what they want

Attitude to specific behaviourBehavioural intention (intend to quit)

Behaviour (Quitting)

Subjective Norms

Evaluations of TRAAdvantages It has been successful in predicting people s eating behaviours. It takes people s individual beliefs and characteristics into account. It has been used to influence the eating behaviour of families, particularly recently in the UK.

DisadvantagesIt doesn t take into account perceived control over actions Intentions don t always predict actions Doesn t take into account previous experience which might influence the way we eat. Doesn t consider irrational decisions. Measurement and testing of attitudes is done via self report which isn t always reliable.

Theory of Planned Behavioury This theory was made by Ajzen (1985). y It is a social-cognition model that states that perceived

behavioural control affects whether a person will perform an action. For example, a person could want to eat more veg because they know it is healthy, but could believe that it costs too much so they can t afford to buy more.

y The stronger the attitude, and the greater the feelings

of control, the more likely a person is to perform the action.

Theory of Planned BehaviourAttitude towards behaviour

Subjective norms

Intention

Behaviour

Control beliefs

Evaluations of TPBAdvantages It has been successful in predicting people s eating behaviours. Shepherd and Stockley(1985) found it to be the best predictor of table salt use.

DisadvantagesIntentions don t always predict actions

Doesn t take into account previous experience which might influence the It takes people s individual beliefs and way we eat. characteristics into account. Doesn t consider irrational decisions. It has been used to influence the Measurement and testing of attitudes eating behaviour of families, is done via self report which isn t always particularly recently in the UK. reliable.

The Health Belief Modely The HBM was developed by Becker in 1974. y It assumes that the likelihood of individuals engaging in health damaging behaviour (such as overeating or drinking) depends on : How susceptible to the addiction they think they are. How susceptible to the diseases associated with the behaviour they

think they are. How severe the consequences of the associated disease areAdvantages Takes personal characteristics into account. There is supporting evidence, particularly in relation to things such as safe sex and HIV. It has real life implications. Disadvantages There is conflicting evidence. It overestimates people s own rationality. The reinforcing effects of addictive behaviour are not taken into account.

Factors that influence eating behaviour

Culturey It is difficult to define the term food , except to say that it is what we eat in

order to obtain nutrients. After all, we have all heard the stories about women craving things like coal but most of us would not consider that to be food . y In different cultures, different things would be considered as food. For example, in India where a lot of people are Hindus, cows would not be considered food but in the UK cows are used commonly as food. y It is likely that classical and operant conditioning are powerful in this context. For example, if someone associates food like ice cream with happy hot days, they may eat ice cream more. However, someone who eats too much ice cream and is sick afterwards may not eat ice cream at all. This is known as one trial learning.y Garcia used rats who have a strong preferance for sweet things to show how

people learn through association. He gave the rats a choice between sweetened water and normal water. All the rats chose sweetened water but each time they drank it, he then gave them a dose of radiation to make them sick. When given the choice again, only 10% of rats chose the non sweetened water, even after a long period of time. y Stannic et al found that children who ate in an environment where fruit and veg were always encouraged were more likely to eat more healthily later in life.

Socio-economical factorsy These are factors that have a direct influence on our eating behaviour. Examples include education, income, cost and religion. y North and Emmet (2000) found that parents that were more educated about proteins, carbs and vitamins were more likely to eat healthily. y Xie et al (2003) showed that children and adolescents from high income families were more likely to have a balanced diet y Donkin et al (2000) stated that accessibility is also an important factor as healthier food tends to be more expensive when available in towns and cities compared to those in outskirts. y Certain ethnic groups and religions do not eat certain foods, for example, Muslims do not eat pork.

Family Influencesy Children s food related knowledge, preference and

consumption are related to their parents beliefs and attitudes, although some evidence suggests that there is also a genetic basis for food preference.

y Researchers at the University of Minnesota found that

children aged 11-18 who ate with their family were more likely to eat fruit and veg. y Research shows that the shaping of food choice is due to family and friends who give the child encouragement when they eat certain types of food. y Duncker (1938) found that children are more likely to try unfamiliar food after watching a parent or close family member eat it.

Health Concernsy Some people alter their diet because they have problems with

their diets, whilst others alter it to avoid problems and some people are just unaware of health issues to do with food.y In the UK, 98% of women aged between 18 and 40 have tried

to diet.y The media also adds to people s health concerns by

highlighting risks for example, recent advertisements about eating the daily recommended intake of fruit and veg.

Moody We all know that our mood affects the way we eat. For

example, sometimes when we are sad we will comfort eat, or if we re feeling extremely low we might not eat at all.y Garg et al found that happy people tend to treat pleasurable

products such as buttered popcorn and chocolate as mood threatening and therefore avoid them whilst sadder people use them as a mood lifter. y Tice et al found that people tend to respond to stress by eating more fatty foods. y Michaud et al found that the stress of an upcomming exam increased the food intake of children by up to 30%.

The success and failure of dieting

Restraint Theoryy Ogden (2003) suggested that if you restrain yourself from doing y

y y 1. 2. 3.

something, you are more likely to over do it. Herman and Mack (1975) got participants to take part in taster sessions. They split the participants into 2 groups. One group received a high calorie taster, and the other received a low calorie starter. The group with the high calorie starter tended to eat more during the test. Ruderman and Wilson also found that dieters tend to actually end up eating more than non dieters. Wardle and Beale (1988) found that dieters tend to over eat for 3 reasons: Counter regulation eating more after high calorie intake Disinhabition eating more because they re being less strict on themselves. What the hell effect seeing eating a piece of chocolate as a failure, so deciding to start the diet tomorrow .

Restraint Theory Boundary Modely Herman and Polvy came up with the Boundary model.

Hunger keeps food intake above a certain minimum whilst satiation keeps food intake below and maximum. y Dieters make their own boundaries inbetween these, but sometimes go beyond and continue until they are full rather than just eating more healthier foods until they are full. y This is thought to be because of physiological factors such as hunger, as well as education and dieting technique.

Evaluations of the Restraint TheoryAdvantagesCombines psychological and physiological factors. Has high face validity Experimental nature is high in reliability.

DisadvantagesPessimistic. If obese people try to diet with restraint, they will fail and then over eat. Thus, over eating may be consequence of dieting. Can not explain prolonged restricting behaviour of anorexics. The experimental nature is low in ecological validity.

Cognitive Shiftsy Over eating has been described as a shift in the dieter s

thoughts. It often involves a breakdown of self-control or a motivational collapse .y Interviews with dieters support this as they stated that

they could no longer be bothered to diet as it took too much effort to eat outside their usual routine.y Sometimes dieters even over eat as an act of rebellion.

Moody Research has shown that dieters in a poor mood tend

to over eat to cause a temporary heightened mood to mask their negative mood. This is the masking hypothesis , commonly known as comfort eating .

y Polivy and Herman (1999) used two groups of

participants, non dieters and dieters. They then told them they had either passed or failed a test. Afterwards, they presented them with unlimited amounts of food. Those who were in the dieters fail group ate more than all the other participants.

Denialy Wegner et al told participants not to think about a

white bear. They had to ring a bell when they thought about the bear. He told other participants to think about the bear. Those who were told not to think about the bear rang the bell more than those who were told to think about the bear. y Ogden found a similar thing happens with dieters. When denying themselves something it has the opposite effect.

Biological Explanationsy Mark (2006) suggests that diets fail because they do

not take into account the biological problems to do with leptin that regulates appetite. y Lapasky et al (2007) suggest that obesity is linked to low levels of leptin.Advantages Takes blame away from the failing dieters. Helps adapt new dieting techniques. Disadvantages Doesn t explain why obesity is a growing problem in the modern world. Not a problem in animals. Not a problem in undeveloped countries.

SUCCESS!!y Dieters tend to succeed when attention is paid to what

is in the meal rather than just eating less. y They also succeed when there is a routine and healthy eating programme rather than a diet . y In a meta-analysis, Higgins and Gray (1999) found that diets were successful when the dieter experienced 3 things: 1. Improved self-esteem 2. Improved behaviour 3. Weight Stability

Biological explanations for eating Neural Mechanisms

Neural Mechanismsy Cannon (1927) thought that hunger came from the stomach. To

prove his theory, he conducted a study in which he swallowed a balloon attached to a cord via which he could pump up the balloon. When the balloon was in his stomach, he blew it up to see if he would get hungry. He found that whilst the balloon was blown up, he did not feel the urge to eat. y Lashley (1938), on the other hand, argued that neural mechanisms play a role in making decisions about when or when not to eat. He studied this by getting a group of rats and removing sections of the brain before putting them in a maze to find food. He found that the lateral hypothalamus was the hunger centre and the ventromedial hypothalamus was the satiation centre .

Duel Centre TheoryThe duel centre theory states that the body has develo ed two systems to control eating behaviour. The lateral hy othalamus turns eating on, and the ventromedial hy othalamus turns eating on. The LH is activated by high levels of ghrelin and low levels of nutrients. The VHM is triggered by high levels of glucose and low levels of ghrelin.Feelings of hunger. Eating starts.

LH feeding centre is activated.

Increase in blood glucose levels. Ghrelin levels decrease.

Feeding sto s. utrient levels begin to decrease.

VHM Satiety centre activated.

Duel Centre Theoryy There is a lot of evidence to support the duel centre theory. y Anad and Brobeck(1951) found that lesions in the LH of rats decreased their eating. However, after a couple of weeks, eating returned to normal. y Lashley found that rats whose VHM was damaged developed over eating. y HOWEVER Gold(1973) found that lesions restricted to the hypothalamus alone had no effect on eating behaviour and only produced over eating when lesioning other areas.

Set Point Theoryy This theory states that everyone has a set weight which

they regulate around.y This theory has face validity as some people can not

seem to lose or gain weight, or return to roughly the same weight after losing/gaining weight.y This theory also takes blame away from people who

just don t seem to be able to lose or gain weight.

Role of Ghreliny Ghrelin is a hormone which is released when the stomach is empty. y Cummings et al (2004) measured the ghrelin levels of participants every 5 minutes whilst participants assessed their own hunger level every 30 minutes. In 5 out of 6 participants, there was a significant correlation between levels of ghrelin and their perceived hunger level. y Ghrelin injections have also been shown the lower the food intake levels of animals. y Gastric bands that are used in treating obesity have been found the reduce ghrelin secretion.

Role of Leptiny Leptin is a fat hormone that signals caloric storage is high. The ventromedial hypothalamus responds to high levels of Leptin and causes feelings of satiation/fullness. y Zhang et al (1994) gave some mice 2 copies of a gene for obesity. These mice tended to over eat. When injected with leptin, they stopped eating as much. y London and Baicy (2007) gave leptin replacement to 3 adults with the obesity gene. This normalised their body weight ad reduced brain activity in eating related areas. y Studies showed that 30% of obese people had leptin deficiency, thus ate more before they felt full.

Neurotransmitters that increase hungery Neuropeptide Y has been found to increase eating

when found in the hypothalamus. y Rats injected with Neuropeptide Y continued to eat way beyond their previously consumed amount.y Norepinephrine (NE) causes eating if injected into

the paraventrical nucleus. It has also been found to reduce eating if injected into the perfornical area.

Neurotransmitters that decrease hungery Chloecystokinin (CCK) has been found to decrease

appetite and suppress weight gain.y Rats injected with Bombesin, a peptide, stopped

eating for prolonged periods of time.y Serotonin is a neurotransmitter that decreases food

intake.

Evaluations of Neural MechanismsAdvantagesOffers an insight into brain chemicals. Helped develop medical interventions. Provides a explanation to some differences in eating behaviours. Studies involving lesions supports the role of the hypothalamus. Much scientific evidence. Reductionist as it doesn t take into account feelings of control and issues people have with certain types of food. Biological determinism takes out factors such as culture, mood or influence. Conflicting evidence of eating disorders. Highly controlled experiments lack ecological validity. Physiological drives can be over ridden. Sometimes we eat when we are not hungry and people restrain from eating whilst on diets.

DisadvantagesLot of animal studies which are unethical and can not be generalised to human beings.

Biological explanations for eating Evolutionary Adaptations.

Taste Preference Faty Stevens and Price (2000) argue that people find it hard to escape evolutionary pressure on food preference. Hence nowadays people struggle with issues such as obesity. y Birch and Deysher (1985) provided evidence in preschool children. When given a preload taste of a high calorie or low calorie meal, those with the high calorie snack tended to have a low calorie meal. y From this they concluded that people have a natural preference for high calorie foods. This has now become maladaptive because we have a high availability of such foods.

Taste Preference Meat/Umamiy Smil (2003) states that the presence of animal fat in meat is what makes it palatable. y Goudstlom (1992) suggests that the use of controlled fire increased meat consumption due to the benefits of roasting and smoking (taste, easier to eat etc) y Stanford(1992) origins of human intelligence are due to meat eating. The development of intellect required for social sharing of meat lead to the expansion of the brain. EG tool making, language, communication. y Finch and Stanford (2004) say that humans gained a select advantage by eating diverse foods.

Taste Preference Sweety Sweet things are associated with the idea of ripeness. y The high concentration of sugar is advantageous to us,

as well as informing us that it s not poisonous. y De Araujo et al (2003) genetically engineered mice to lack the sweet tasting gene. He then supplied them with sweetened water and non sweetened water. They preferred the sweetened water despite not being able to taste it. This suggests that preference of sweet things is not based on the taste, but on the calorie count.

Taste Preference Salty Fesseller (2003) pointed out that salt is advantageous

when water is scarce as it prevents sudden dehydration.y Beauchamp (1987) found that 2 year old children

reject food that contains too much salt, or not enough salt.

Taste Aversion Sour and Bittery Sour things suggest that things are poisonous. We are

more sensitive to bitter and sour things. We have 27 receptors for bitter tastes but only 2 for sweet tastes. y Mannella(2008) children reject medicine on basic biology. Children are more sensitive to bitter tastes. y Simmen and Hladic (1998) suggest that this shows a evolutionary importance for identifying poisonous food. y Garcia (1966) studied taste aversion in rats (in earlier slides). Taste aversion aids survival.

Food Neophobiay This is the fear of tasting new things. y This is thought to be an adaptation formed to avoid

eating harmful things.y Kheapila et al (2007) conducted a twin study and

found that there is a genetic basis to food neophobia.

Cookingy Cooking has been adapted to kill bacteria as well as

make food more tender and easier to digest.y This means that we use less calories eating cooked

meat than we would eating raw meat.y As a result of this, our molars have decreased in size.

Spicesy Spices have anti-bacterial properties and tend to be

used more in hotter countries.y This seems to be because more spices preserved the

meat, so in a hot climate in which food would go off very quickly, meat would be preserved.

Morning Sicknessy Profet suggests that morning sickness is an

adaptation to protect a vulnerable foetus from natural toxins.

y Taxman and Sherman (2000) looked at the results of

56 morning sickness studies covering 76,000 in 10 different countries. They found that the food most likely to cause morning sickness in meat eating cultures are: meat, fish, poultry and eggs. These are the foods most likely to be contaminated with parasites or bacteria.

Evaluations of Evolutionary AdaptationsAdvantagesOffers an valid explanation to food preferences and behaviour. Shows similarities with other species. Evolution of teeth and organs support the theory. Can explain unusual food preferences such as morning sickness and cravings.

DisadvantagesLots of research with children so can not be generalised to everyone. Ignores the role of society. Nature or Nurture?

Anorexia Nervosa

Anorexia Nervosay There are four DSM-IV criteria for Anorexia Nervosa: 1. The individual has a body weight less that 85% of that 2. 3. 4.

expected. There is an intense fear of becoming fat. The individual s thinking about their body weight is distorted, either by exaggerating its size or by minimising the dangers of being underweight. In females, the absence of three of more consecutive menstrual cycles (amenorrhoea).

y In the UK, 90% of women aged between 15 and 50 are unhappy

with their bodies, and 98% of women aged between 15 and 50 have attempted to diet. But why don t all these women develop anorexia?

Anorexia Nervosa Biological Explanations

Neurotransmittersy Increase in serotonin which suppresses appetite. y Increase in dopamine.Positive Bailer et al found higher levels of Serotonin in AN patients compared to control patients. Kaye et al (2001) found that drugs were successful in preventing relapse in recovering AN patients. Wang et al (2001) found lower levels of dopamine in obese people. Adolescents with AN tended to have high levels of H acid, a waste product of dopamine. Negative We can not tell whether high levels of serotonin and dopamine are caused by AN or are what cause it. Drugs have been unsuccessful in treating current sufferers of AN, suggesting that more is at play.

Dysfunctions in the Hypothalamusy Damage to the lateral or ventromedial hypothalumusPositive Negative

Studies on rats in which parts of the Most research has been conducted on hypothalamus has been damaged. Results rats and therefore can not be generalised show change in eating behaviour. (In to humans. earlier slides) Humans with tumours in regions of the hypothalamus often suffer from excessive binging or loss of appetite.

Neural Developmenty Significant association between premature birth and development of

AN. y Season of birth suggests that damage caused by viruses in maternity can result in AN.Positive Mindberg and Hjem found that a high percentage of anorexics were born at least 3 weeks premature. Eagles (2001) found that people born in spring are much more likely to develop AN. Willoughby et al found significantly lower levels of AN in countries where it is hot all year round. Negative

Not everyone who was born prematurely develop AN. Not everyone born in spring develop AN. AN does not affect animals who normally give birth in spring. Countries that have warmer seasons all year round tend to have a different culture to ours, so perhaps it is culture rather than seasons.

Geneticsy There has been research suggesting that genetics often

plays a role in the development of AN.Positive Holland et al (1984) found a high concordance rate between MZ and DZ twins. Kortegaard et al found that identical twins are likely to share the same disorders. Suggests contribution but not cause. Negative If AN was due solely to genetics, the concordance rate between MZ twins would be 100%. Twins share the same environment, not just the same genes, especially MZ twins who often have identity conflict. Many twin studies contain small samples. Immigrants who come from countries in which AN does not exist sometimes develop AN even though their family didn t have it.

Evolutiony AN causes women s periods to stop, therefore delaying pregnancy. y An adaption so that we could flea from predators.Positive Supported by ancient migration patterns. Takes blame away from the sufferer. Negative Evolutionary approach states that we must reproduce. Most AN patients die without reproducing. Doesn t account for anorexia in males.

General CriticismsAdvantagesHelped develop treatments such as drugs and therapies. Takes blame away from the sufferer. Has a lot of objective supporting evidence.

DisadvantagesReductionist ignores other factors such as psychological aspects. Determinist states that behaviour is shaped by internal factors that can not be altered. Cause or effect?

Anorexia Nervosa Psychological Explanations

Behavioural Approachy Classical conditioning

learning to associate food with anxiety. y Operant conditioning reinforcement of dieting and weight-loss as good behaviours. y Social learning Vicarious reinforcement of dieting and being thin as good behaviours. Positive Negative Alberge (1999) found a high incidence of anorexia in occupations where pressure is put on appearance. Barlow and Durland (1955) found that over half of contestants in a Miss America contest were only 85% of their expected body weight. Fearn(1995) studied a group of women in Fuji who did not have western TV. After they got access to TV, 75% of the Fujian women said they were too big . This model doesn t take into account any of the faulty thought processes such as thinking you re bigger than what you are. People stop getting rewarded for losing weight when family and friends start to be concerned about appearance. Eysenk and Flanagan (2000) pointed out that everyone is exposed to the pressures by the media but only 3-4% of people develop AN.

y Faulty thinking or faulty processes cause AN. Eg, misconceptions of the body or

Cognitive Approach

irrational beliefs about food. y Cognitive errors, such as over generalising failure or control, or magical thinking eg if I reach size 0, everyone will like me. Positive Negative Patients with eating disorders tend to misconceive their actual body size. Fallon and Rozin (1985) found that women tended to rate themselves bigger than their actual size and much bigger than their ideal. McKenzie et al (1993) noted that anorexic patients overestimated their body size by much more than a control group of women. Their ideal weight was much lower than the control group and after a small snack they judged themselves to have put on weight. Is faulty thinking a symptom of AN or the cause? Lots of women who are dissatisfied with their bodies don t turn anorexic.

y Symptoms symbolise repressed conflicts and motives in the unconscious mind due to

Psychodynamic Approach

a traumatic sexual experience in childhood. EG wanting to have a pre-pubescent body because they don t want to grow up and have adult relationships. y Bruch (1973) said AN is caused by ineffectual parents. Positive Negative Wonderlich et al surveyed 1099 American women and found those with a history of sexual abuse were more likely to develop an eating disorder. Romans et al (2001) pointed out that early maturation and parental over control were risk factors for the development of AN. Salzman (1997) said that children with anxious resistant attachment were most likely to develop anorexia. Not all anorexics have had a traumatic sexual experience, nor have all victims of sexual abuse developed AN. Could be that they have issues such as low self esteem linked to their abuse. This has nothing to do with wanting to remain childlike. Lack of objective evidence. Doesn t account for the increase of anorexia unless more people are being abused. Physical states such as being hungry are innate, not learnt. Often use retrospective data

General CriticismsAdvantagesHelped develop treatments such as counselling. Offers hope as thought processes and behaviour can be changed and relearnt. Has a lot of objective supporting evidence.

DisadvantagesReductionist ignores other factors such as biological aspects and trends. Cause or effect?