The effect that food and eating have upon our pleasure receptors has been of great interest in studying the nature of pleasure. What we eat depends on personal preferences, but most importantly the availability of certain foods. Due to economic development, it is now possible to obtain almost anything that one desires. Supermarkets, local convenience stores and restaurants now cater for almost any pleasurable palate meaning easy access. As well as a change in how we access our food, a change has also become apparent in the effects that consumption has upon our health. There has been an epidemiological shift from acute (such as food poisoning) to long-term (heart diseases) health problems. Because of a modern busy lifestyle, convenience foods are of common practice and fast food stores produce food that is of high sugar and fat. According to Jeffrey et al (2006), 1 billion people are overweight, 300 million are obese, 18 million of which are under the age of five, which is repeatedly linked to the consumption of fast food. It has also been found that variety in a diet can lead to weight gain. Under Rozin’s (1999) philosophy, “food is both a pleasure and a poison”. However, what about the consequences?
With high medical and aesthetic standards for body image, body dissatisfaction and weight concerns are increasing. In a study by Rozin (2003), it was found that 57% of females and 21% of males (n=2100) have a high concern about their own weight, 13% so much that they are too embarrassed to even purchase chocolate in a shop.
However, these effects of indulging oneself in pleasurable consumption are not found cross-culturally.
Perhaps the most famous example is the French paradox, observed by Rozin (1999, 2003, 2005). When compared to the USA, the French consume more animal fat and alcohol, yet the prevalence of cardiovascular disease is about 30% less in the French. 68% of US males and 51% of US females have a BMI (body mass index) of 25 or above, compared to 49% of French males and 35% of French females.
Rozin attempted to provide multiple explanations for this phenomenon. Firstly, although French diets are typically higher in fat, they are also lower in calories and the US generally have proportionally larger portion sizes. Secondly, eating is considered to be a rather important part of everyday life in France. The French concentrate more on the eating experience which means that they experience less stress and more pleasure in relation to eating. These positive social associations are not seen as much in the US who tends to focus more on the consequences of eating instead of the experience itself. And thirdly, energy expenditure is of great contrast between the two countries. In France it is more common to walk or cycle to a shop or town whereas in the US it is more common to drive. In this case then, it would be advisable to recommend countries like the United States to adopt an attitude and lifestyle more like the French when it comes to eating.
Why is that we eat and why is it that some people just can’t stop eating? The main physiological mechanisms that influence our eating behaviour are appetite (the desire to eat), hunger (the need to eat), satiation (feeling full) and satiety (length between meals). The glucostat hypothesis states that glucose receptors (glucostats) in the liver and the lateral hypothalamus measure blood glucose and the rate at which the glucostats fire is related to the level of glucose in the extracellular fluid. A drop in glucose levels produces a signal which consequently induces food seeking and consumption.
The desire to eat can also be explained biologically by the glucose cycle which states that we eat because the cells in our body require glucose of which we obtain through eating. In the glucose cycle carbohydrates are broken down into glucose and all cells use glucose as a nutrient. Any excess glucose is stored as glycogen in the liver or muscles, or as triglycerides in adipose tissue which can be released again with the help of glucagon. Triglycerides can be broken down by fatty acids and glycerol. Glucose can only be absorbed by cells when insulin is secreted; however, the rate at which insulin is secreted is different for different nutrients (simple carbohydrates produce a quicker secretion rate than proteins).
Satiation (the end of the consumption stage) mechanisms involve the gastric fill (the feeling of repletion in the stomach) and nutrient specific receptors in the stomach and liver and fat receptors in the duodenum. Satiation normally becomes apparent when positive feedback from food in the mouth and negative feedback from receptor activation and the gastric fill is equal. However, satiation also depends on the energy density of foods. Satiation mechanisms for proteins are quick and relatively strong, whereas satiation mechanisms for fats are slow and weak. Blundell (1991) stated that if a meal is high in fat content then the satiation mechanisms are weak and slow which leads to “passive overeating”.
Food preferences vary culturally and individually. Cultures have a large influence on what is considered to be pleasurable food or not, this can be a cause of availability, genetics or religion. However, because of the quantity and variation of taste receptors in each individual human are different then the experienced taste is also different depending on what taste receptors one possesses. According to Miller and Reedy (1990), the greater number of taste receptors, the more intense the reported taste experience.
The consequences of excessive food consumption may cause weight gain which in turn could lead one to exercise in order to counterbalance these effects. Kaplan et al (1982) interviewed people who exercise regularly and found that they did so for a number of reasons. The first and most obvious reason was to maintain a healthy body, however, other responses included that it helped reduce anxiety and stress levels. This finding was in support with Harris (1981) who found that when asked, psychological benefits of exercising are given just as much as physiological ones.
It has been suggested that a moderate programme of physical activity can cause a reduction in both trait and state anxiety (Raglin, 1997). However, Bahrke & morgan (1978) found evidence that supports the ‘change of pace’ hypothesis which states that exercise simply provides the opportunity to reflect on, or forget ones troubles and has no stronger a therapeutic effect than meditation.
Studies have suggested that exercise is as powerful as personal hardiness (Kabosa, 1979) in buffering the negative effects of stress. Holmes (1985) supports the notion of exercise as a buffer against stress in finding that physically fit people report fewer stress related health problems and fewer symptoms of depression. In addition, Theyer, Newman and McClain (1994) found that a lot of people view exercise as the most effective strategy for reducing tension and eliminating negative mood states. A majority of studies have also found evidence that reveal a positive correlation between exercise and self-esteem (Sonstroem, 1984; 1987). However, such a relationship is difficult to make due to the multiple variables that could lead to such a correlation such as enhanced body image and an increased feeling of self control.
Due to the current economic situation, many people are now choosing to exercise outdoors instead of at a gym. This can be linked back to what was mentioned earlier about the effects of nature so that an exercise done outside, such as jogging through the countryside or hiking up a mountain should be a highly pleasurable activity for one to do. The fact that people do such activities out of their own free will supports this. Other activities done outside such as weeding and mowing the lawn, which are not necessarily carried out as a means of exercise, have been shown to have psychological benefits. An American study on life satisfaction (Waliczek et al, 2005) found that gardeners showed higher life satisfaction scores, especially for zest for life, physical self concept and energy levels as opposed to non-gardeners. Kaplan derived the attention restoration theory in attempting to explain the benefits of nature. The attention restoration theory consists of four components; being away (frees up mental activity); extent (a coherent other world); fascination (requires involuntary attention); and compatibility between activity in new environment and individual purpose. From this it can be suggested that gardening acts as a form of escapism from everyday life, leaving behind the troubles and woes of everyday life, which in turn can be psychologically beneficial to people’s mental states.
The benefits of physical exercise are thoroughly understood and accepted and have been recognised for centuries. These include lower rates of coronary heart disease, blood pressure and strokes. The main mental health benefits of exercise include reduced anxiety and stress, enhanced mood and cognitive function and increased self worth (Biddle et al, 2000). Lack of physical exercise can even lead to diseases such as type-2 diabetes and hypokinetic disease which are health problems cased by or related to a lack of physical exercise (Kraus & Raab, 1961). Due to the increasing government concerns about population weight gain, the British Government has even started a new initiative aimed at families. ‘Change4life’ recommends up to 60 minutes of exercise per day and its slogan is “eat well, move more, live longer’, however, does this really lead to a happier life?
There has been relatively recent interest in the notion of a ‘feel good factor’ as the main reason for exercise. Evidence that comes in support of this comes from Bryne & Bryne (1993). They conducted a major review of literature on exercise and found that 90% of the studies done on exercise and depression reported antidepressant effects. Scully et al (1998) conducted a similar analysis of 80 studies and found positive support for a relationship between exercise and depression. However, some controversy around the ‘feel good factor’ remains such as, how frequently does one need to exercise in order to feel good about oneself?, or what sort of exercise would lead to feelings of pleasure? These also lead to measurement concerns as how can such feelings be measured? Nevertheless, Biddle et al (2000) drew the conclusion that “overall, the evidence is strong enough for us to conclude that there is support for a causal link between physical activity and reduced clinical define depression”. However, there is much speculation as to what the causal link could be.
Social theorists would claim that exercising with or around others helps reinforcing existing relationships or helps build new social relationships which in turn may be the factor that helps combat/ prevent depression.
Other theories include the boosting of self esteem as exercise involves learning new skills and achieving goals, the accomplishment of which along with an enhancement of body image could lead to increased perceived self worth.
However, biological accounts would claim that exercise can lead to an increased release of endorphins, enkaphalins and other chemicals that promote feelings of well-being and also pain relief. It is well known that endorphins’ major function is a pleasure peptide (Hawkes, 1992). The phenomenon of runners ‘high’ has also been investigated (Hawkes, 1992). Some runners report a euphoric state in which they feel an increased sense of well being, an increased pain tolerance and an addiction to exercise which has been compared to the state of euphoria which is aroused by opium intake. Yet, with this phenomenon, problems of definition and scientific validity arise.
The cognitive neuroscience approach explains the causality with the transient hypofrontality approach (Dietrich, 2006). This approach claims that in order to run motor patterns, assimilate sensory inputs and coordinate autonomic regulation, extensive neural activation is required which causes a transient decrease of neural activity such as the prefrontal cortex. This sort of exercise induced hypofunction can provide a coherent account of the influenced that exercise has on emotion and cognition.
But what sorts of brain mechanisms are characteristic of emotion? Bord (1929) conducted a study on sham rage (an exaggerated, poorly directed aggressive response of decorticate animals) and found that with the removal of the cerebral hemispheres and hypothalamus, sham rage was not elicited. This lead to the suggestion that the hypothalamus is critical for the expression of anger and the cortex has a function of inhibiting and directing such an emotion.
The amygdala has also been found to play a large role in danger-detection and fear. Adolphs (1994, 1999) found that patients with Urback-Wiethe disease (amygdala damage) had an impaired ability at evaluating fearful facial expressions. Brain imaging studies have found that activity in the amygdala increases in response to fearful facial expressions (Breiler et al, 1996). However, it remains unknown which brain structure is responsible for pleasure. Pleasurable emotions are generally an understudied topic compared to the study of negative emotions mainly because pleasure is so difficult to define. Pleasurable emotions involve multi-sensory processing, complex motor response and several cognitive processes which make it very difficult to locate a specific brain region that is responsible for it.
In this sense it would appear that pleasure requires a lot of effort from nearly every part of the brain whereas negative emotions require much less effort from more specific evolutionary regions such as the hypothalamus. It could be suggested that negative emotions do prevail over positive emotions which is why mood disorders such as depression exist. Going back to Charles Darwin, the possibility that positive emotional states evolved to counter-balance the prevalence of negative emotions would make sense. The pursuit of happiness is now becoming more common as more people are setting out in life not to be rich or have a respectful job but to be simply happy; a life well lived. However, happiness is not as easy to obtain and even maintain as people would like to think but is instead a complex cognitive state that requires a great deal of effort and is influenced by countless various factors. It was the Austrian psychotherapist Viktor Frankl who once said that a life devoted to the ‘pleasure principle’ could only ever have a thin and depleted consciousness. This suggests that the pursuit of pleasure does not always yield the desired results, but can in fact have detrimental effects. It would seem that in order to achieve a happy state one must aim for more than happiness. Frankl wrote ‘What man actually needs is not a tensionless state but rather the striving and struggling for a worthwhile goal, a freely chosen task…’ Don’t aim to achieve happiness, aim to simply achieve.
However, a point that requires attention and is possible the most influential factor in pleasure obtainment is the simple fact of individual differences; what one person would gain pleasure from doesn’t necessarily mean someone else would acquire just as much (if any) pleasure in the same thing.
References
Frankl, V. E. (1959). Man’s search for meaning. Boston, Massachusetts: Beacon Press.
Kringelbach, M.L. & Berridge, K.C. (In-press). Towards a functional neuroanatomy of pleasure and happiness [Electronic version]. Trends in Cognitive Sciences.
Gullone, E. (2000). The biophilia hypothesis and life in the 21st century: Increasing mental health or increasing pathology? [Electronic version]. Journal of Happiness Studies, 1, 293-321.
Ray, J.J. & Lovejoy, F.H. (1984). Attitude toward the environment as a special case of attitude toward all living things [Electronic version]. Journal of Social Psychology, 123, 285-286.
Waterman, A.S. (1993). Two conceptions of happiness: contrasts of personal expressiveness (eudaimonia) and hedonic enjoyment [Electronic version]. Journal of Personality and Social Psychology, 64, 678-691.
Wilson, E. O. (1984). Biophilia: The human bond with other species. Cambridge, Massachusetts: Harvard University Press.
Ulrich, R. S. (1993). Biophilia, biophobia, and natural landscapes. In S. R. Kellert
& E. O. Wilson (Eds.), The biophilia hypothesis (pp. 73–137). Washington, DC:
Shearwater.
