Eating

• Esophagus - connects the mouth to the stomach
• Liver - cleans the blood & removes toxins
• Stomach - short term food store
• Gall Bladder - stores & excretes bile which breaks down fat
• Pancreas - makes insulin & glycogen to regulate blood sugar levels
• Small intestine - chemical digestion of food & absorption of nutrients into the blood
• Large intestine - absorbs water from the remaining indigestable food & transmits the uesless waste from the body
• Appendix - no known function - evolutionary function to eat grass & bark
• Rectum - stores faeces

Social Learning

• Impact of observing others - parental modelling of attitudes to food affects children's own attitudes. Brown & Ogden found correlations between parents and their children in terms of snack food intake, eating motivation & body disatisfaction.
• Media effects - MacIntyre et al found the media has a major impact on what people eat and their attitudes to certain foods. However, many attitudes (e.g. healthy eating) are limited by personal circumstances (e.g. income & age). Therefore people learn attitudes from the media, but then place these within the broader context of their lives.

• There is research support - Meyer & Gast surveyed 12 year olds & found a positive correlation between peer infleuence & disordered eating. 'Likeability' of peers was the most influential factor. Birch & Fisher found that the best predictors of daughters' eating behaviour were their mothers' dietary restraint & their perception of the risk of their daughters becoming overweight.
• Attitudes are about much more than just learning - Social learning explanations focus exclusively on how children acquire attitudes towards eating from exposure to models (e.g. in the media). However, evolutionary explanations suggest that our preference for fatty & sweet foods is the direct result of an evolved adaption. 
• IDA - There is a gender bias - Most studies have focused solely on women's attitudes to eating behaviour, yet research has shown that homosexual men are also at risk of developing disordered eating attitudes & behaviour, including body dissatisfaction & higher levels of dieting than heterosexual men. 

Cultural Influences

• Ethnicity - Research suggests that body dissatisfaction and related eating concerns & disorders are more characterisitic of white than black or Asian women. Ball & Kenardy studied 14,000 Australian women of various ethnic origins. The longer they had spent in Australia, the more they reported eating-attitudes similar to Australian-born women (the acculturation effect).
• Social class - Body dissatisfaction and eating concerns are more common among middle & higher class individuals. Dornbusch et al surveyed 7000 American adolescents and found that higher class individuals had a greater desire to be thin and were more likely to be dieting to achieve this, than were lower class individuals. 

• There is research that challenges ethnicity influences - Mumford et al found more evidence of body dissatisifaction and eating disorders among Asian schoolchildren than among their white counterparts. Another researcher found more evidence of a 'drive for thinness' among black girls than among white girls. 
• There are cultural differences - Rozin et al explored the way food functions in the minds of people in 4 different cultures. Americans tended to associate food with health, whereas the French associated it with pleasure. Females of all 4 cultures had attitudes more similar to those of the Americans. Cultural background influences attitudes to eating & therefore means the measurement of attitudes in one culture tells us little about attitudes of a different culture.
• There is research that challenges social class influences - The relationship between social class & attitudes to eating is not as straightforward as suggested by Dornbusch's study. In a sample of American students, Story et al found that higher social class was related to greater satisfaction with weight & lower rates of weight control behaviour. 
• There are problems with generalisability - Some studies in this area are from clinical populations, some sub-clinical & some non-clinical. This makes it difficult to generalise from one group to another & draw valid conclusions about the causal factors in attitudes towards eating. 

Mood and Eating Behaviour

• Binge-eating - Individuals with bulimia experience anxiety prior to bingeing. The same relationship between anxiety and binge-eating appears to hold for sub-clinical populations as well. Wegner et al found that people who binged had a low mood before and after binge-eating. Although low mood may make binge-eating more likely, it does not alleviate the low-mood state.
• Comfort-eating - Garg et al observed food choices of participants as they either watched an upbeat movie or a depressing one. 'Happy' participants chose healthy food (grapes) but 'sad' participants went for the short-term pleasure of junk food (popcorn).

• The reinforcing qualities of binge-eating are not clear - Although a number of studies have shown that low mood tends to precede a bing-eating episode, any reinforcement is fleeting and many studies report a drop in mood immediately after the binge. As a result, it is difficult to see what the reinforcing qualities of a binge-eating episode might be. 
• Comfort eating may not work - Our attitude towards comfort foods such as chocolate is based largely on the belief that it can lift our mood. However, a study by Parker et al found that chocolate, if used repeatedly, is more likely to prolong a negative mood than to alleviate it. This challenges the view that low mood causes comfort-eating, because comfort-eating may not be that effective in overcoming a low mood.

Dieting is the main consequence of body dissatifaction (when may be real or imagined). The majority of dieters are women, and as many as 87% of all women have dieted at some time in their lives (Furnham and Greaves).

Ogden suggests several possible factors for women's dissatifcation with their bodies:

• Media Influence
• Family
• Ethnicity
• Social Class
• Peer groups & social learning

Does dieting work? The short answer is no. Some women can lose weight simply thrugh dieting and maintain that weight loss. However, most women cannot, and even more bizarrely they often end up eating more. 

Disinhibition

Restrained eating have become synonymous with dieting, but Herman & Mack's restraint theory suggests that attempting not to eat may actually increase the probability of overeating. It is the disinhibition (loss of control) of restraint that is the cause of overeating in restrained eaters. Wardle & Beales randomly assigned obese women to 1 of 3 groups for 7 weeks; restrained eating, exercise or non-treatment. Women in the restrained eating group at more than women in the other two groups. 

The Boundary Model

This model explain the failure of dieting in terms of the greater distancce between hunger and satiety in dieters. It takes dieters longer to feel hungry and therefore more good to reach a state of satiety. In addition, dieters have a self-imposed desired intake. Unlike non-dieters, when they go over this threshold of desired intake, they experience a 'what the hell' effect, and continue to eat until they reach satiety, i.e. beyond the maximum level imposed as part of their diet. 

• Restraint theory has limited relevance - Ogden argues that restraint theory may explain the overeating of some groups with disordered eating patterns (e.g. dieters, bulimics & some anorexics). However, the behaviour of resricting anorexics (where weight loss may be achieved by restricting calories) cannot be explained in this way. If trying to not eat results in overeating, claims Ogden, then how do restricting anorexics manage to starve themselves?
• Obesity treaments based on restraint may fail because the restraint theory suggests that restraint leads to overeating, yet the treatment of obesity typically recommends restraint as a way of losing weight. As a result, overeating may be a consequence of obesity treatment, leaving many obese individuals depressed, feeling a failure & unable to control their weight. 
• IDA - There is a cultural bias in obesity research because some cultural groups appear to find it harder to diet successfully because of a natural inclination to obesity. Asian adults are more prone to obesity than Europeans. Asian children & adolescents have a great central fat mass compared to other ethnic groups.
• Psychology as a science - the limitations of anecdotal evidence - Many studies of dieting success or falue rely on personal accounts & this evidence is then used to justify claims about particular dieting strategies. However, such anecdotal evidence has 2 problems that properly controlled scientific studies do not have: the main limitation is that memory is not 100% accurate & assessment of the success or failure of dieting tends not to be objective. Both these create problems for the reliability of anecdotal accounts.

The theory of ironic processes of mental control

Attempting to suppress a thought frequently has the opposite effect, making it even more prominent. 

Central to any dieting strategy is the decision not to eat certain foods. This results in a state of denial as dieters attempt to suppress thoughts about foods 'forbidden' as part of their diet.

Wegner suggests any attempt to suppress thoughts of forbidden foods only increases the dieter's preoccupation with the very foods they are trying to deny themselves. As soon as food is denied, therefore, it becomes more attractive. 

• There is research support - Soetens et al found that participants who suppressed thoughts about food also showed a rebound effect, and were more likely to think about food after suppression. This might explain why denial of thoughts about food leads to greater rather than less preoccupation with it.
• IDA - Free will or determinism - born to be fat? Some people find dieting ineffective because they have high levels of lipoprotein lipase (LPL), which make the body more effective at storing calories. This would challenge the view that restraint or denial alone could be effective as a means of losing or maintaining weight. 
• There may be gender different in LPL activity - Research suggest that sex hormones play a part in LPL activity. For example, oestrogen inhibits LPL activity, which explains why women put on weight after menopause when oestrogen levels are lower. A consequence of this is that dieting through restraint or denial may be more difficult for post-menopausal women for purely biological reasons.

Fending off boredom

Redden claims that people usually like experiences less when they have to repeat them constantly. When it comes to dieting, this makes it harder to stick to a particular regime. However, by focusing on the specific details of each meal, people get bored less easily and are better able to maintain their diet. 

• IDA - Real world application - This has led to the development of anti-diet programmes aimed at replacing dieting with conventional eating. These emphasis regulation of eating by body hunger & satiety signals rather than the development of inappropriate attitudes to food (e.g denial or retraint), which ahve been shown to be inffective at weight control. A meta-analysis fo the effectiveness of anti-dieting programmes (Higgins & Gray) found that they could improve both eating behaviour and psychological wellbeing, and led to weight stability rather than weight change. 

Homeostasis

Homeostasis involves mechanisms that detect the state of the internal environment and also correct it to restore that environment to its optimal state. 

The body has evolved two homeostatic mechanisms to regulate food intake, both dependent on glucose levels.

• Hunger increases as glucose levels decrease
• A decline in glucose levels activates the lateral hypothalamus (LH) resulting in feelings of hunger
• This causes the individual to search for and consume food, causing glucose levels to rise again
• This activates the ventromedial hypothalamus (VMH), leading to feelings of satiation and a cessation of feeding.

• There are limitations to a homestatic explanation - For a homestatic hunger mechanism to have been truely adaptive, it must anticipate & prevent energy deficits, rather than just react to them . The claim that feelings of hunger and eating behaviour are only triggered when energy resources fall below their opitmal level is inconsistent with the harsh environment in which this mechanism would have developed. A buffer against lack of future food availability would have been neccesary in such circumstances. 
• IDA - An evolutionary approach - Evolutionary theorists offer an alternative explanation. They propose that the primary influence of hunger and eating is not homeostasis, but food's positive-incentive value i.e. people eat because they develop a taste for foods that promote their survival. 

Role of the Hypothalamus

• Lateral hypothalamus (LH) - Research discovered that damage to the LH in rats causes aphagia (absence of eating). Stimulation of the LH brings about feeding behaviour. Neuropeptide Y (NPY) is important in turning on eating behaviour. When injected into the LH of rats it causes them to immediately start feeding, even when satiated. Repeated injections of NPY cause obesity in just a few days.
• Ventromedial hypothalamus (VMH) - Damage to the VMH causes hyperphagia (overeating) in rats. Stimulation of this area inhibits feeding. Damage to VMH also causes damge to the paraventricular nucleus (PVN). It is now believed that damage to the PVN causes hyperphagia. Reeves & Plum performed a post-mortem examination of a patient who had doubled her body weight in 2 years. They found a tumour in the VMH which caused her to over eat.

• Reductionist - focuses exclusively on biological apects of hunger & satiety
• Deterministic - focuses exclusively on the role of nature & no space left to choice, cultural & social influences. There is subsantial & convincing evidence that social, cultural & psychological factors affect our eating behaviours as is evident for psychological explanations of eating disorders. 
• Use of animals - in research implies the lack of generalisability (ethics) 
• Validity - highly controlled laboratory experiments may lack ecological validity
• There is a problem with the LH explanation - Marie et al genenetically manipulated mice so that they did not make NPY, yet found no subsequent decrease in their feeding behaviour.
• IDA - Real world application - Yang et al found that NPY is also produced by abdominal fat. This leads to a vicious cycle where NPY produced in the brain leads to more eating and the production of more fat cells, which in turn lead to the production of more NPY. By targeting individuals at risk of increased levels of NPY, it should, therefore, be possible to treat obesity. 
• There is a problem with the VMH explanation - Gold claimed that lesions to the VMH alone did not produce overeating, but did so only when these lesions included the PVN; however, subsequent research failed to support Gold's findings. As a result, it is now acknowledged that aniamls with VMH lesions eat more & gain weight rapidly. However, in humans, the PVN has another function i.e. to detect the specific foods that our body needs which may account for many food 'cravings'. 

The environment of evolutionary adaptation (EEA)

EEA refers to the environment in which a species first evolved. The adaptive problems faced by our ancestors in the EEA would have shaped early food preferences. For most of human history, human beings would have lived in hunger-gatherer societies, which would have led to to a preference for high-calorie (for energy) and easily available foods.

Early diets

Preference for fatty foods was adaptive because harsh conditions in the EEA meant that for early humans energy resources were vital to stay alive. Early humans evolved a preference for foods that were particularly rich in calories (fatty foods, sweet foods) because these promoted survival. These preferences for calorie rich goods persist among modern humans, despite the fact that such foods are not particularly nutritious. 

Preference for meat

Good for brain growth - a meat diet was full on densely packed nutrients & therefore provided a catalyst for the growth of the brain. As a result, humans were able to evolve into the active & intelligent species that they became. By supplying all the essential amino acids, minerals and nutrients needed to stay active & alive, this allowed early humans to supplement their diet with widely available, but less nutritious, plant-based foods. 

Sherman and Hash suggest that the reason we likely our meat spicy is because the spice has antibacterial properties. They looked at over 7000 recipes from 36 countries. This could explain why in hot climates, people use more spice in their food.

Taste Aversion

Taste aversion was first demonstrated by Garcia et al. Rats, made ill through radiation after eating saccharin, developed an aversion to it because they formed an association between the illness & the taste of saccharin. 

Adaptive advantages - taste aversion would have helped our distant ancestors to survive, because if they survived after ingesting poison then they could learn to avoid that food in the future. Once learned, taste aversions are difficult to shift, an adaptation that would have helped survival.

The medicine effect describes a tendency for individuals to develip a preference for any food eaten just before recovery from an illnes, which then becomes associated with feeling better. 

We like sweet stuff

Harris found that new born babies have a preference for sweet things and a dislike for bitter things. These preferences are universal - so they suggest a genetic link. Sweet food triggers the pleasure centre of the brain, through the release of dopamine. This acts as a reinforcer. Most poison was a strong bitter taste - this could be a genetic survival reflex.

We won't eat mouldy bread

We have learned to avoid food which seems unripe and mouldy. Knowledge passed on from people to people as well as through our own experiences tells us that good food means life and bad food means death. 

• Reductionist - evolutionary explanations reduce food prefereneces solely down to evolution and our ancestors and ignores any biological explanations for food preferences
• Deterministic - argues that food preferences are due to our ancestors and we have no free will - we can determine our own food preferences
• Takes the nature side of the nature/nurture debate - argues that food prefence is due to our environment and not our genetics
• Evolutionary explanations can be tested - by studying a related species that faces similar adpative problems. After starving for much of the year, chimpanzee go straight to the fattiest parts of their kill. 
• Not all food preferences can be traced back to EEA - some modern preferences (e.g. low-cholestrol foods) could not have evolved during the EEA because they had no beneficial effects for our ancestors. Similarly, many things that were important to our distance ancestors (e.g. high-fat foods) are more likely to be avoided by modern humans because they are now know to be damaging to health.
• There is research that supports preference for fatty foods - Gibson & Wardle found the best way to predict which fruit/veg would be preferred by children was to measure how calorie-rich they were. Bananas & potatoes are rich in calories & were most preferred by 4-5 yr olds. This supports the claim that humans have evolved preference for calorie-rich foods.

• Early humans might have been vegetarian - Cordain et al claimed that early humans are more likely to have found most of their calories in sources other than saturated animal fats (meat). However, evidence has shown that all societies show a preference for animal fats, suggesting that this is a universal evolved preference. It is also unlikely that early humans could have found sufficient calories for an active lifestyle from a vegetarian diet. 
• Cultural factors are also important in food preferences - It is likely that many food preferences (e.g. for spicy foods) developed because of cultural tastes & preferences. However, although cultural differences do exist, they are usually a fine-turning of evolved food preferences that are found in all cultures.
• Taste aversions can be explained by biological preparedness. Differential learning abilities in different species means that each species has the ability to learn certain associations more easily than others, particularly associations that help them survive.
• IDA - Real world application - Research on the origins of taste aversion has been used to help understand the food avoidance that ofter occurs during chemotherapy. This claim was supported in a study which gave patients a novel-tasting ice cream prior to their chemotherapy and the patients subsequently developed an aversion to that ice cream. This has led to hospitals giving patients both a novel & a familar food prior to their chemotherapy. Aversion then forms to the novel food & not to the familar food. 

People with anorexia try to keep their weight as low as possible, usually by restricting the amount of food they eat. They often have a distorted image of themselves, thinking they are fat when they're not. People affected by anorexia often go to great attempts to hide their behaviour from family and friends by lying about eating and what they have eaten, or by pretending to have eaten earlier.

Clinical characteristics of anorexia nervosa:

• Intense fear of becoming fat
• Refusal to eat, despite hunger
• Restrictive eating & restrictive calorie intake
• Malnutrition & starvation
• Stops having periods
• Body weight below 85% of expected
• Obsessive exercising
• Perceives self as overweight, even when seriously underweight

Cultural ideals & the media

• Cultural ideals - Western standards of attractiveness are thoguht to contribute to body dissatisfaction, a distorted body image and AN. Gregory et al found that in the UK, 16% of girls ages 15-18 were dieting. 
• Media influences - the portrayal of thin models on TV & in magazines is a significant contributory factor in body image concerns & the drive for thinness among Western adolscent girls. Jones & Buckingham found people with low-self esteem are more likely to compare themselves to idealised images portrayed in the media. 

Ethnicity & Peer Influences

• Ethnicity - Other cultural groups place less emphasis on thinness in women, e.g. the incidence of AN in non-Western cultures & black populations in Western cultures is much lower. In many non-Western cultures, there are more postive attitudes towards large body sizes, which are associated with attractiveness & fertility. 

• Peer influences - Einsberg et al found that dieting among friends was related to unhealthy weight control behaviours. Teasing about overweight girls or underweight boys may serve to enforce gender-based ideals concerning weight.

Psychological factors & personality

• Bruch's Psychodynamic theory distinguished between effective parents who respond to their child's needs, and ineffective parents who fail to respond appropriately. Children of ineffective parents grow up confused about their internal needs and become overly reliant on their parents. During adolescence these children strive for independence, but are unable to achieve this without taking excessive control over their body shape & developing abnormal eating habits. 
• Personality - Two personality characteristics commonly associated with AN are perfectionism & impulsiveness. Strober et al found high levels of perfectionism in 73% of boys with AN and 50% of girls with AN. Butler & Montgomery found that patients with AN responded more rapidly and innaccurately on a task than did a control group. 

• IDA - Ethical issues in AN research - Researchers are increasingly using anorexia chat rooms & newsgroups to gain qualitative data from those who actually have AN (or care for those with the disorder). This creates significant ethical issues for the researcher, particularly in relation to invasion of privacy, lack of informed consent and a breach of confidentiality. 
• There is research support for media influences - A study of adolescent Fijiangirls found that after the introduction of TV to the island, these girls stated a desire to lose weight and to be like the women they saw on Western television. However, other research has shown that the media can and does have an effect on the development of disorded eating and AN, but these effects can be avoided.
• IDA - Real world application - Because the media has such a powerful influence on eating behaviour in young people, the fashion industry in France has repsonded by pledging to use a diversity of body types and not to stereotype the 'thin ideal'.
• Not all research supports ethnic differences in AN - Research shows that the view that white populations have a higher incidence of AN than black populations is only supported among older adolescents (Roberts et al)

• Not all research supports the role of peer influences in AN - Shroff & Thompson found no correlation among friends on measures of disordered eating in an adolescent sample. Although Jones & Crawford did find support for the claim that overweight girls & overweight boys are more likely to be teased and so they develop disordered eating patterns. These gender differences did not emerge until adolescence. 
• There is support for Bruch's psychodynamic theory - Steiner found that parents of adolescents with AN had a tendency to define their children's needs rather than letting them define their own needs. This supports the claim that children of ineffective parents become overly reliant on their parents to identify their needs. Supporting the lack of control claim, Button and Warren examined a group of AN sufferers 7 years after they were diagnosed with the eating disorder. These individuals relied excessively on the opinions of others & felt a lack of control over their own lives.
• There is support for the perfectionism claim - Halmi et al found that women with a history of AN scored higher on a scale of perfectionism, & the extent of perfectionism was directly related to the severity of AN experienced by these women. 
• A genetic explanation for the perfectionism/AN link - Halmi et al also studied relatives of people with AN & found that perfectionism as a trait appears to run in families. This suggests that perfectionism represents genetic vulnerability for the development of AN.

Neural Explanations

• Serotonin - Disruption of serotonin levels leads to increased anxiety, which may then tigger AN. Bailer et al found high levels of serotonin in women with binge-eating/purging AN, with highest levels in those with the most anxiety.
• Dopamine - Increased dopamine activity in the basal ganglia alters the way people interpret rewards, so individuals with AN find it difficult to associated good feelings with things that are usually pleasurable (e.g. food).
• Season of birth - Individuals with AN are more likely to be born during spring months. This may be due to infections during pregnancy or temperature at the time of conception.
• Pregnancy & birth complications - Inadequate nutrition during pregnancy among mothers with an eating disorder may act as a diathesis for the development of AN in the child. Lindberg and Hjern found an assocation between birth complications and the development of AN. Birth complications may lead to brain damage due to lack of oxygen, impairing neurodevelopment of a child. 

Evolutionary explanations

• Reproduction suppression - Females in the ancestral environment had a delayed onset of sexual maturation when conditions were not conducive to their offspring's survival. AN may be a variation of this adptation, causing females to alter the timing of their reproduction when they feel unable to cope with the biological, social and emotional responsibilities of adulthood. 
• 'Adapted to flee' famine hypothesis - Typical AN symptoms of food restriction, hyperactivity and denial of starvation reflect evolved adaptation in response to local famine conditions. When individuals lose weight, adaptive mechanisms usually cause conservation of energy and an increase in desire for food. This adaptation must be 'turned off' so that individuals increase their chances of survival by moving to a more favourable environment in terms of food resources. 

• A problem for the serotonin explanation - SSRIs, which alter levels of serotonin in the brain, are ineffective when used with AN patients. However, some studies report that SSRIs may help to elevate mood & reduce some of the obsessive symptoms of anorexia.
• There is research support for the dopamine explanation - Castro-Fornieles et al found that adolescent girls with AN had higher level of HVA (a waste product of dopamine). However, Wang et al found that obese individuals had lower than normal levels of dopamine, suggesting an inverse relationship between levels of dopamine & body weight.
• There is research support for season of birth explanation - Eagles et al found that AN individuals tend to be later in birth order than healthy individuals. They may be at a greater risk of being exposed to common infections from their siblings during the critical period of brain development in the second trimester of pregnancy.
• There is research support for pregnancy & birth complications - Favaro et al found that the perinatal complications assoicated with a risk of developing AN were; obstructed blood supply in the placenta, early eating difficulties and low birth weight. 
• Biological explanations can reduce parental feelings of guilt - An advantage of these explanations is that people realise they are dealing with a dysfunctional biology (which is treatable), rather tahn a dyfunctional family (which isn't) This reduces guilt felt by many parents that they caused the development of AN in their child. 

• IDA - Biological determinism - a real world application - Research in this area has implications for insurance payouts for psychiatric conditions which do not regard AN as 'biologically based' and therefore not liable for a payout. 
• There is research support for reproduction suppression - This explanation is supported by the observation that the onset of puberty is delayed in prepubertal girls with AN. Additionally, because the absence of periods is a typical characteristic of AN, this mean that reproduction is suspended in AN females. 
• IDA - Gender bias - The reproduction suppression account of AN does not explain why AN would develop in men. According to recent statistics, 25% of adults with eating disorders are male, suggesting that AN is not solely a female disorder and therefore cannot be explained just in terms of the suppression of reproduction.
• There are limitations of evolutionary explanations of AN - We might question how the symptoms of AN would've been passed on through generations through natural selection, particularly as AN decreases fertility and makes reproduction more difficult, and may even kill the individual with this condition.