Weight loss and diet maintenance are at the forefront of health discussions and the United States has reached an all time high for obesity rates. Biopsychology, which is the study of the biology of behavior, has begun to focus on the mechanics behind hunger and eating by researching hunger and consumption theories and the positive-incentive perspective of eating. This theory offers the most opportunity to understand all biopsychosocial behaviors associated with eating, nutrition, and diet maintenance. Opposing theories, such as the set-point theories, are discussed as well as the implications of the positive- incentive theories on behavioral psychology. In closing, recommendations for further research are discussed.
The United States, as well as most developed countries, is obsessed with weight and body image and the ideal body image today is thin and perhaps at a lower body mass index than what is considered to be healthy (Ahern & Hetherington, 2006). Given that the United States has reached an all time high for obesity rates the fact that millions of Americans are focused on weight control and diet maintenance should not come as a surprise (Winter, 2005). Biopsychology,which is the study of the biology of behavior, has begun to focus in detail on the mechanics behind hunger and eating by researchinghunger and consumption theories and the positive-incentive perspective of eating (Pinel, 2006). There are a variety of theories, both supported and unsupported by research, regarding hunger and consumption that are used to explain weight loss, gain, and stability. For example, historically people believed that the stomach was in control of the bodily function of managing hunger and weight (White, 2006). However, that theory was disregarded when research using patients who had their stomachs removed still expressed a sensation of feeling hungry (Oxford University Press, 2007). The set-point theory suggests that there is a natural weight that a person's body feels comfortable and that is why most adults maintain a stable size throughout life (Harris, 1990). However, this theory does not account for the fact that most adults do have weight variation and that other factors contribute to how much a person eats, what his or her metabolism rate is, and whether or not he or she will avoid eating disorders such as obesity. The positive incentive perspective does account for theses factors and presents a variety of theories to suggest that humans eat because of influences including social situations, routine and desirability of the food type, anticipated pleasure factors, and biologicalfactors (White, 2006).
Biopsychology and Hunger and Nutrition In order to understand these theories the mechanics behind digestion needs to be addressed. Biologically thehuman body is set up to run efficiently using the natural processes of the desire for food and the nutritional benefit to the body. Digestion officiallybegins in the mouth by the chewing of food to prepare it for digestion. After swallowing food,it flows down the esophagus, through a valve that connects the esophagus to the stomach, and nextit enters the upper part of the stomach (NIH, 2004). The lower stomach then mixes the food, liquid, and digestive juice that is produced in the stomach.The food is then pushed into the small intestine in which nutrients are pulled from food throughout the digestive process (NIH, 2004). Finally, the unabsorbed matter is pushed into thecolon and it is expelled through a bowel movement. Hormones, such as ghrelin which is produced in the stomach and upper intestine, are said to stimulate appetite with the absence of food, and other amino acids such as peptide YY which is produced in thegastrointestinal tract is said to repress appetite (Il,1993). Additionally there are nerves thatregulate the speed in which this process occurs. In addition to the mechanical part of digestion there are the cephalic, absorptive, and fasting phases that occur to help the body metabolize energy. In the cephalic phase the body prepares for food that is about to be absorbed by releasing small amounts of insulin, and this phase is triggered by the expectation of food and the tasting and chewing offood (Teff, 2000). The anticipation and expectation of eating occurs and is furthered through sight, smell, and perhaps even cooking sounds (Toray & Cooley, 1997). Insulin levels begin to riseduring the cephalic phase and glucose levels are typically low.
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Biopsychology: Positive-Incentive Perspectives and Diet Maintenance
