Hunger-Meaning biological , psychosocial, genetic factors
OPTIMAL WEIGHT : The reason you never see fat wolves is that they, like all animals, have an inherited biological system that carefully regulates their eating so that they maintain their optimal, or ideal, weights (Kolata, 2000b).
OPTIMAL or IDEAL WEIGHT- results from an almost perfect balance between how much food an organism eats and how much it needs to meet its body’s energy needs.
OVERWEIGHT means that a person is 20% over the ideal body weight.
OBESITY means that a person is 30% or more above the ideal body weight.
THREE HUNGER FACTORS
- Biological hunger factors- come from physiological changes in blood chemistry and signals from digestive organs that provide feedback to the brain, which, in turn, triggers us to eat or stop eating.
- Psychosocial hunger factors come from learned associations between food and other stimuli, such as snacking while watching television; sociocultural influences, such as pressures to be thin; and various personality problems, such as depression, dislike of body image, or low self-esteem.
- Genetic hunger factors come from inherited instructions found in our genes. These instructions determine the number of fat cells or metabolic rates of burning off the body’s fuel, which push us toward being normal, overweight, or underweight.
BIOLOGICAL HUNGER FACTORS
1) Peripheral cues come from changes in blood chemistry or signals from digestive organs, which secrete various hormones. 2)Central cues result from activity in different brain areas, which in turn results in increasing or decreasing appetite.
Peripheral cues : Signals for feeling hungry or full come from a number of body organs that are involved in digestion and regulation of blood sugar (glucose) levels, which is the primary source of fuel for the body and brain.
1 When empty, the STOMACH secretes a hormone, ghrelin, which carries “hunger signals” to the brain’s hypothalamus, the master control for hunger regulation (Ralo, 2005). When the stomach is full, stretch receptors in its walls send “full signals” to the brain’s hypothalamus, which decreases appetite (Chaudri et al., 2006; Kluger, 2007).
2 The LIVER monitors the level of glucose (sugar) in the blood. When the level of glucose (blood sugar) falls, the liver sends “hunger signals” to the brain’s hypothalamus; when the level of glucose rises, the liver sends “full signals” to the hypothalamus (Woods et al., 2000).
3 The INTESTINES also secrete ghrelin, which carries “hunger signals” to the hypothalamus, increasing appetite. The intestines also secrete another hormone called PYY, which carries “full signals” to the hypothalamus, decreasing appetite (Ralo, 2005). Finally, the intestines secrete a hormone called CCK (cholecystokinin), which signals the hypothalamus to inhibit eating (Kluger, 2007).
4 FAT CELLS secrete a hormone, called leptin, which acts on the brain’s hypothalamus. If levels of leptin are falling, the hypothalamus increases appetite; if levels are rising, the hypothalamus decreases appetite. The secretion of leptin helps maintain a constant level of body fat and defend against starving the body to death (Rui, 2005).
The stomach and intestines secrete a number of “hunger” or “full” hormone signals that act on the hypothalamus, which is the master control for regulating eating and produces central cues for increasing or decreasing appetite.
Central cues: 1 The brain has an area with different groups of cells that are collectively called the HYPOTHALAMUS. Each group of cells is involved in a different kind of motivation, including regulation of thirst, sexual behavior, sleep, intensity of emotional reactions, and hunger. We’ll focus on two groups of cells, the lateral and ventromedial hypothalamus, that affect hunger in opposite ways, either increasing or decreasing appetite.
2 THE LATERAL HYPOTHALAMUS refers to a group of brain cells that receives “hunger signals” from digestive organs—increase in ghrelin, fall in level of blood glucose, and fall in levels of leptin. The lateral hypothalamus interprets these “hunger signals” and increases your appetite (Kluger, 2007; Woods et al., 2000). For example, electrical stimulation of the lateral hypothalamus causes rats to start eating, while destruction of the lateral hypothalamus causes rats to stop eating and even starve without special feeding.
3 The ventromedial hypothalamus refers to a group of brain cells that receives “full signals” from digestive organs—a full stomach activates stretch receptors, rise in level of blood glucose, rise in levels of leptin, and increase in the hormones PYY and CCK. The ventromedial hypothalamus interprets these “full signals” and decreases appetite.
GENETIC HUNGER FACTORS
Genetic hunger factors come from inherited instructions found in our genes. These instructions determine the number of fat cells or metabolic rates of burning off the body’s fuel, which push us toward being normal, overweight, or underweight.
1.We inherit different numbers of fat cells.FAT CELLS, whose number is primarily determined by heredity, do not normally multiply except when people become obese. Fat cells shrink if we are giving up fat and losing weight and greatly enlarge if we are storing fat and gaining weight (Fried, 2008; Spalding et al., 2008).People who inherit a larger number of fat cells have the ability to store more fat and are more likely to be fatter than average.
2.We inherit different rates of metabolism. METABOLIC RATE refers to how efficiently our bodies break food down into energy and how quickly our bodies burn off that fuel.For example, if you had a low metabolic rate, you would burn less fuel, be more likely to store excess fuel as fat, and thus may have a fatter body. In comparison, if you had a high metabolic rate, you would burn off more fuel, be less likely to store fat, and thus may have a thinner body . This means that people can consume the same number of calories but, because of different metabolic rates, may maintain, lose, or gain weight. There are only two known activities that can raise metabolic rate: exercise and smoking cigarettes.
3.We inherit a set point to maintain a certain amount of body fat.The set point refers to a certain level of body fat (adipose tissue) that our bodies strive to maintain constant throughout our lives.For example, a person whose body has a higher set point will try to maintain a higher level of fat stores and thus have a fatter body . In comparison, a person whose body has a lower set point will maintain a lower level of fat stores and thus have a thinner body (Woods et al., 2000).
4.We also inherit weight-regulating genes.Weight-regulating genes play a role in influencing appetite, body metabolism, and secretion of hormones (leptin) that regulate fat stores.
PSYCHOSOCIAL HUNGER FACTORS
Learned Associations : The best examples of how learned associations influence eating are when we eat not because we’re hungry but because it’s “lunchtime,” because foods smell good, because our friends are eating, or because we can’t resist large portions (Hellmich, 2005).
Social-Cultural Influences : Obesity rates vary across the globe: Japan, 4%; Italy, 10%; France, 11%; Germany, 14%, United Kingdom, 24%, and United States, 34% (OECD, 2009). Here are examples of how social-cultural influences affect body weight.
Personality & Mood Factors : If a person has certain personality traits, he or she may be at greater risk for overeating as well as developing serious eating disorders, such as overeating when stressed or depressed, going on food binges (bulimia nervosa), or starving oneself (anorexia nervosa).Mood factors, such as stress, anxiety, and depression, can lead to bursts of overeating or indulgence in sweet and unhealthy foods. Overeating when under emotional strain is called “emotional eating” and occurs in otherwise healthy people (Macht, 2007).
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