Hunger, eating and health PDF

Preview

Summary

Required essay for the course....

Description

Hunger, Eating and Health For Biopsychology (PSY3311) M-W: 10:00am – 11:15am Presented to Dr. Matiko Bivins by Tra Nguyen April 16th, 2014

Hunger, Eating and Health Eating is one of the few things we do every single day. It is a behavior that is of interest to virtually everybody. We must eat to live, to sustain the human body and supply energy for bodily processes. We all do it, and most of us derive great pleasure from it. This is a fairly simple concept but however, for many of us, eating becomes a source of serious personal and health problems. This paper will demonstrate hunger from every perspective, explain the theories of hunger and also, focus on some eating-related health problems and eating disorders. First of all, the question "Why do we feel hungry?" seems to be very obvious to answer. It is because we need to get nutrients to survive. Hunger is the motivation for us to be able to know that we need to get the nutrients in our body. But how do we really know that we are hungry? The answer can be analyzed by three different components: biological, learned, and cognitive. Many theories of hunger are historically discussed from the biological component. The first influential study of the physiological basis of hunger was conducted in 1912 by Canon and Washburn. He swallowed a balloon on the end of a thin tube, the balloon was partially inflated, and a pressure gauge was attached to the other end of the tube each time that he had a large stomach contraction, Washburn reported a pang of hunger; this led to the view that stomach contractions are a major factor in hunger. But the finding that animals whose stomachs had been enervated or completely removed ate enough to maintain their body weights discredited this view. In addition, people with no stomachs report feeling hungry and maintain their body weights; they eat less per meal, but they eat more meals. More recently, Koopman has used a second-stomach preparation to implicate the gut in feeding behavior. Rats who have had a second stomach implanted into their peritoneum eat less when the second stomach is loaded with food, even though the stomach is not innervated nor are the nutrients able to be absorbed into the

bloodstream. Following with that, the glucostatic and lipostatic theories of hunger has been heavily influenced by the idea of a feeding set-point, based around the idea of a homeostatic, negative feedback system regulating feeding. It has been strongly influenced by the idea that feeding is controlled by deviations from two different set points: a set-point for blood glucose (short-term regulation) and a set-point for body fat (long-term regulation). According to this assumption, a person's energy resources are thought to be at or near their set-point soon after eating, and to decline after that. Once the person's energy levels fall below a certain threshold, the sensation of hunger is experienced, which is the body's way of motivating the person to eat again. Therefore, the set-point assumption is a negative feedback mechanism

Hunger cannot truly be explained only by the biological component. As human beings, we cannot ignore our psychological part, the learned and cognitive components of hunger. Unlike any other beings, human use an external clock in our daily routine, including when to sleep and when to eat. This external time triggers our hunger. For instance, when the clock says 12 pm, lunch time, many people feel hungry just because it is lunch time. This hunger is triggered by learned behavior. In addition, the smell, taste, or texture of food also triggers hunger. For instance, if you like french fries, the smell of frying potatoes may trigger your hunger. However, this preference of taste, smell, or texture is a culturally learned preference. If one does not like sushi, the smell of sushi does not trigger hunger. Interestingly, people also feel hungry for a particular taste, more specifically, the four basic tastes: sweet, sour, bitter, and salty. For example, an often heard expression is "I am staving for something sweet." People keep feeling hungry until these four tastes are satisfied. Besides, colors also contribute to hunger. Looking at a yellow banana makes us want to eat it, but a red banana does not. Similarly, red or green can trigger hunger for an apple, but not blue. Blue is said to be an appetite suppressant. So color

greatly affects our hunger. Moreover, many people eat foods base on their knowledge of what foods are good for them. For example, low fat, low sugar, and low sodium food are said to be good. Eventually people learn to change their preference and want to eat "good food" only. These concepts are related to the positive-incentive theory, which is based on the idea that we eat because eating is pleasurable, rather than to satisfy some set point for glucose level or fat level. When our favorite food is present, we will eat; regardless of whether we actually need the food or not. Humans need energy and nutrients in order to survive and will respond to feelings of hunger and satiety. Different macronutrients have different effects on satiety. For example, fat is the least satiating, followed by carbohydrates then protein. In addition, low energy density diets have greater satiety than high energy density diets. The mechanism of hunger and satiety are not necessarily the same. There are two mechanisms for satiety. One is at the brain level, the other is at the gastrointestinal tract level. There are two places in the hypothalamus, part of the brain that controls hunger and eating. The Ventromedial Nuclei gives a signal when to stop eating, and the Lateral hypothalamus gives a signal to start eating. We feel satiety at the brain level because of the function of the Ventromedial Nuclei. On the other hand, at the level of the gastrointestinal tract, satiety signals come from the stomach, which controls short-term eating.

Most eating-related health problems are associated with eating too much or too little. There are mainly three kinds of eating disorders: Binge Eating, Anorexia Nervosa, and Bulimia. Although several cultural and physiological correlates of eating disorders have been identified, the fundamental causes of these disorders remain a mystery. Binge eating is characterized by one's eating a very large amount of food until she or he feels uncomfortably full. This binge eating is done when one is not hungry. According to the DSM-IV (American Psychiatric Association, 1994), Anorexia Nervosa has two types: restricting type, and binge-eating/purging

type. Anorexia Nervosa restricting type is when one extremely restricts food intake, and it is not followed by binge-eating or purging behavior. On the other hand, Anorexia Nervosa bingeeating/purging type was described as one engaged in purging and binge-eating regularly. A common symptom of Anorexia is one's putting her or himself on self-starvation to avoid feeling fat or gaining weight. Although people with this disorder weigh far below normal, they still think they are overweight. Eventually they are at risk of losing their lives due to malnutrition. People with this disorder still feel hungry, yet they cannot eat because they are too afraid of gaining weight. Physiological causes of this disease are not yet clear, although there are some findings showing a connection with serotonin and norepinephrine. The learned component of Anorexia cannot be ignored. Studies show that there is more Anorexia in Westernized cultures than other cultures; because the social value of slimness pushes people to be thinner. Cognitively, these people have a distorted body image of themselves, and dissatisfaction with their own body image, which is influenced by the cultural value of slimness, and leads to eating disorders. Bulimia Nervosa is a condition of binge eating followed by purging and use of laxatives. Unlike Anorexia, people with this disorder are normal or above weight. Psychologically, having quilt and shame are common symptoms among people with Bulimia. Unlike anorexic people who put absolute control over restricted eating, bulimic people cannot control their eating. The physiological cause of Bulimia is still unclear. Psychologically, Bulimia is said to be linked to depression and anxiety, but clear evidence of causation has not yet been found. Cognitively, people with Bulimia are said to be motivated to escape from reality by binging. It is possible that those people were given food by their caretakers to lift their mood in their childhood. Like Anorexia, cultural learning that one needs to be thin to be accepted may also contribute to the cause.

In America, more than half of the adult population is classified as clinically obese; adversely, there has been a similar rise in eating disorders related to not eating enough: roughly 3% of the teen and adolescent populations are diagnosed as anorexic. These are staggering statistics, but what are the implications? At some point in your life, you or someone close to you will develop an eating disorder. At its simplest, there are two primary factors in obesity: energy input and energy output. That said, there are several factors that can contribute to the possibility of obesity. Though not frequently the case, genetics can contribute to obesity; however, more likely influences involve cultural influences, strong personal preference for certain high-calorie foods such as fatty or sweet tastes, familial influence that promotes excess eating, and abnormally strong responses to the thought, sight, or smell of food. Energy output is different for everyone; the most obvious thought that comes to mind is in regard to the amount of exercise one gets. However, there are other factors that affect energy output, including: the basal metabolic rate, diet-induced thermogenesis (reaction to fat increases), and non-exercise activity thermogenesis (fidgeting, maintaining posture, or degree of muscle tone). The prevailing belief about eating and hunger is that the body's eating system is designed to trigger hunger when energy levels are low, and once one has eaten and energy levels return to normal, one's hunger is satiated. This is the "set point" theory that proposes the body works very much like a heating system in which an internal "thermostat" controls hunger and satiety.

However, if the set point theory were true, eating disorders would be nearly obsolete; instead, the number of those suffering from eating disorders continues to grow. One major contradiction to the set point theory is supplied by looking at human evolution. Our ancestors faced some significant issues when it came to eating; in particular, food supplies were not abundant, as they are today, and they were far from predictable. To survive, our ancestors had to

eat as much as possible when food was available so that extra calories could be stored as fat to ensure survival until the next meal was procured, in much the same way as bears, groundhogs, and other hibernating creatures store fat to survive the winter. Another contradiction to the setpoint theory is that it does not account for the myriad variety of factors that contribute to hunger and eating, such as taste preferences, environment, and learned behaviors. These issues are addressed by the theory of positive-incentive perspective. Positive-incentive theory basically states that eating is triggered by the anticipated pleasure the eating provides, and that the level of hunger felt is based on the interaction of a variety of factors, including: flavors, length of time between meals, amount and composition of food previously eaten, blood glucose levels, environment, and previous experiences with the food. One primary selling point for the positiveincentive perspective is its comparison to sexual behavior: one does not have a set-point for sexual release or sexual expression that must be made up when a deficit occurs. Instead humans have evolved to desire sexual release and expression simply for the pleasure derived from such activities. The argument here is that humans have evolved to desire food and eating for the pleasure derived from the tastes, textures, and flavors of food, among other factors. The positiveincentive perspective, at its most basic, means that eating is triggered by the anticipation of the pleasure that eating provides. It is believed that persons who suffer from anorexia have experienced the opposite effect. In other words, for anorexics, the positive-incentive value of food has dropped or is non-existent, even though the person may seem to be obsessed with food. Sweet, salty, and high fat foods have become preferences for many through evolution, since these foods are associated with high-calorie and sodium-rich foods.

The types of foods we choose are also based on learned taste preferences or aversions. Some taste preferences are learned through the flavor of milk excretions during breastfeeding

and culturally specific foods. Equally important are factors that influence how often one eats. The frequency that one eats is affected by one's socio-economic situation, cultural norms, schedules and routines, habits, and personal preferences to name a few. There are also factors at work that influence how much one eats; primary of these are the satiety mechanism which sends signals based on the volume and calorie content of food consumed that causes one to stop eating. Appetizers or small amounts of food consumed prior to a meal increase hunger. One's environment also plays a part in how long it takes one to feel satiated. Studies have found that 60% more is consumed when eating with others; this is not taking into account the excess of calories one consumes when distracted by activities such as watching television. Particularly in humans, social environments can also have the opposite effect, in that often humans will not eat as much as they are accustomed to in social settings. Sensory-specific satiety is the taste-specific effect that positive-incentive food offers. A variety of tastes during a meal (the cafeteria diet) influences how much is eaten. Cafeteria diets are, for the most part, taste-specific. When one food is eaten, positive-incentive for that food bottoms out, while the positive-incentive for other foods also drops. Yet, cafeteria diets can lead to an increase in caloric consumption through the effect of the variety of foods that offer differing tastes. Some research that has been conducted by Woods points to the aversive physiological effects that meals can have, which may be more powerful in individuals who have not been eating very much. The physiological effects of meals are the disruption of the homeostatic balance in the body when it receives a sudden influx of calories. Additionally, society's belief that meals, versus small snacks throughout the day, are the "normal and healthy" way of eating leads to many anorexics being forced to eat, which causes conditioned taste aversions. Repeated conditioned taste aversions only serve to strengthen the anorexic's desire to not eat. There are many factors that can contribute to the incidence of

obesity, anorexia nervosa, and other eating disorders, and there are numerous factors that influence hunger and satiety. Learning about the physiological aspects behind hunger and satiety and the factors that contribute to eating disorders may help increase your understanding of eating disorders and perhaps which direction future treatment will take.

Hunger is a primary motivation. Despite strong beliefs that hunger is caused biologically, this motivation is controlled not just by physiology, but also psychology as well. What makes human beings different from animals is we eat not only to feed our bodies to satiate physiological hunger, but also to feed our minds to satiate psychological hunger also. Although these two kinds of hunger interchangeably cause hunger by affecting one another, putting some food in our mouth is not necessarily the right way to feed our psychological hunger. Problems like eating disorders and obesity could occur because we mistakenly keep trying to satiate our psychological hunger by eating food. Thus, hunger is not only about how the body changes physiologically, it is about how our body and mind together are well fed, not just by the food that one can put in their mouth, but also by the whole environment around us.

References Assanand, S., Pinel, J. P. J., & Lehman, D. R. (1998a). Personal theories of hunger and eating. Journal of Applied Social Psychology, 28, 998-1015. Pinel, J. P. J., Assanand, S., & Lehman, D. R. (2000). Hunger, eating, and ill health. American Psychologist, 55, 1105-1116. Cannon, W. B., & Washburn, A. L. (1912). An explanation of hunger. American Journal of Physiology, 29, 441-454. Shepherd R. (1999). Social determinants of food choice. Proceedings of the Nutrition Society. 58: 807-812. Weingarten,H. P. (1985). Stimulus control of eating: Implications for a two factor theory of hunger. Appetite, 6, 387-401. Drewnowski, A.,Halmi, K. A., Pierce, B., Gibbs, J., & Smith, G. P. (1987). Taste and eating disorders. American Journal of Clinical Nutrition, 46, 442-450. Klein, D. A., & Walsh, T. B. (2004). Eating disorders: Clinical features and pathophysiology. Physiology & Behavior, 81, 359-374. Södersten, P., Bergh, C., & Zandian,M. (2006). Understanding eating disorders. Hormones and Behavior, 50, 572 578. Polivy, J & Herman, P. C. (2002). Causes of eating disorders. Annual Review of Neuroscience, 53, 187-213. Redd, M., & de Castro, J. M. (1992). Social facilitation of eating: Effects of social instruction on food intake. Physiology & Behavior, 52, 749-754....