LECTURE OVERVIEWWHY DO WE EAT?

WHY DOES EATING BECOME DISORDERED?

PSYCHOSOCIAL AND BIOLOGICAL FACTORS

OBESITY, ANOREXIA, BULLIMIA

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Why is eating so complicated?

Eating is a motivated behavior, yet it is also confused with emotion and

can become disordered.

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Drive-Reduction Theory

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1. Eating to reduce hunger is a good example of the drive theory of motivation.

2. But the arousal theory of motivation explains why we might eat a slice of pumpkin pie after consuming a heavy holiday dinner i.e. stimulation seeking.

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• Cannon & Washburn’s early technique for measuring internal factors in hunger

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Hunger and Eating

Psychosocial Theories for why eating becomes disordered

• Incentive: motivation results from the “pull” of external environmental stimuli

• Cognitive: motivation affected by attributions & expectations

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Psychosocial Theories for why eating becomes disordered (cont.)

Behavioral: unhelpfullearned associations

Analytical: expression of inner conflict

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Hunger and Eating

• Biological factors: stomach, biochemistry, the brain

• Note the size difference in these rats. The rat on the left had the ventromedial area of its hypothalamus destroyed, the one on the right had

• the lateral hypo.removed.©John Wiley & Sons, Inc. 2010

CHEMISTRY OF EATING?

• Is the ventromedial hypothalamus a satiety center? Is the lateral hypothalamus an eating center?

• Leptin is the hormone that signals satiety in the brain.

• Ghrelin is the hormone that signals hunger in the brain.

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Hunger and Eating• Psychological factors:

visual cues, cultural conditioning

• Or Genetic: Obesity is more common in Pima Indians living in U.S., but not for those in nearby Mexico with traditional diet.

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Is Obesity a Psychological Issue?

• Obesity results from numerous biological and psychosocial factors.

BMI > 30

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• Anorexia nervosa & bulimia nervosa are both characterized by an overwhelming fear of becoming obese & explained by multiple biological & psychosocial factors.

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©John Wiley & Sons, Inc. 2010