Midterm 1- Lesson 1-12 Flashcards
Explain how leptin and insulin control eating behavior.
A number of hormones control eating. Leptin and insulin, in particular, circulate in the blood in concentrations that are proportionate to body fat mass. They decrease appetite by inhibiting neurons that would otherwise stimulate eating. They also stimulate melacortin-producing neurons in the hypothalamus, which inhibit eating.
Describe the role of ghrelin in weight gain.
Ghrelin is secreted by specialized cells in the stomach, spiking just before meals and dropping afterward. It stimulates appetite by activating the neurons that stimulate eating behavior. When people are given ghrelin injections, they feel extremely hungry.
Indicate the effects that ventromedial hypothalamus damage produces in rats.
Rats who have a damaged ventromedial hypothalamus behave like obese humans do. They eat excessive amounts of food, show little sensitivity to internal cues related to hunger (e.g., how long it has been since they last ate), and respond to food-related external cues, such as the presence of food. Although their meals are normal, they eat much more often than healthy rats.
Identify the health risks associated with obesity.
Obesity is defined as an excessive accumulation of fat (more than 20-27% in women and more than 15-22% in men). It increases the risk of cancer, atherosclerosis, hypertension, diabetes, gallbladder disease, arthritis, and heart failure.
Explain why the prevalence of childhood obesity is increasing.
Children have more sedentary lifestyles than they did even a generation ago. Early eating habits are also contributing to this increase in obesity. There is a greater tendency for children to overeat and to be drawn to unhealthy foods because of advertising and marketing pressure.
Compare “apples” and “pears.”
Recent epidemiologic evidence suggests that abdominally localized fat, as opposed to excessive fat in the hips, buttocks, or thighs, is an especially potent risk factor for cardiovascular disease, diabetes, hypertension, and cancer. Sometimes called “stress weight,” abdominal fat increases especially in response to stress. People with excessive central weigh (sometimes called “apples,” in contrast to “pears,” who carry their weight on their hips) are more psychologically reactive to stress and show greater cardiovascular reactivity and neuroendocrine reactivity to stress. This reactivity to stress may be the link between centrally deposited fat and increased risk for diseases.
Discuss the effects of genetics, family history, SES and culture on obesity.
- Genetics: Evidence for genetic factors comes from twin studies, demonstrating that twins reared apart show a tendency toward obesity when both natural parents were obese, even when the twins’ environments are very different. Other studies have shown that children who were later to become obese were distinguished by a vigorous feeding style, consisting of sucking more rapidly, more intensely, and longer, with shorter bursts between sucking. This style produces a higher caloric intake and greater body weight. The fact that the feeding style emerges very early suggests that it may be one of the mediators of a genetic predisposition to obesity.
- Family history: Overweight parents are more likely to have overweight children than are normal-weight parents. For example, one study found that 44% of the dogs of obese people were obese, compared with only 25% of the dogs of people with normal weight. Many factors in a home, such as the type of diet consumed, the size of portions, and exercise patterns, contribute to the obesity that runs in families. The size of a family may influence the extent to which parents can actively manage their children; with fewer children, parents may be able to bring about concerned weight loss in any one child.
- Socioeconomic Status (SES) and Culture: In the U.S., women of low socioeconomic status are heavier than high-SES women, and African-American women, in particular, appear to be vulnerable to obesity. Although SES differences in weight have previously been attributed to high-carbohydrate diets early in life, this account does not explain why SES is not associated with obesity in men and children. One factor may be the simple fact that diets high in fats and sweets cost less than those high in vegetables, fish, and fruit. Thinness is valued among the wealthy and in developed countries, which in turn leads to a cultural emphasis on dieting and on physical activity.
Describe the effects of stress on eating behavior.
- About half of people eat more when they are under stress, and half eat less. For non-dieting and non-obese normal eaters, the experience of stress or anxiety may suppress physiological cues suggesting hunger, leading to lower consumption of food. Stress and anxiety, however, can disinhibit the dieter, removing the self-control that usually guards against eating, thus leading to an increase in food intake both among dieters and the obese.
- Stress also influences what food is consumed. People who eat in response to stress usually consume more low-caloric and salty foods, although when they are not under stress, stress eaters show a preference for high-caloric foods. Stress eaters appear to choose foods containing more water, which gives food a chewier texture.
obesity
An excessive accumulation of body fat, believed to contribute to a variety of health disorders, including cardiovascular disease.
yo-yo dieting
The process of chronically alternative between dieting and regular eating, leading to successive weight gains and losses; over time, yo-yo dieters increase their chances of becoming obese by altering their underlying metabolism.
set point of theory weight
The concept that each individual has an ideal biological weight that cannot be greatly modified.
