Obese Externality
Obese Externality
In the late 1960s, the social psychologist Stanley Schachter (1922–1997) proposed that obese people eat (and overeat) not because of hunger, stress, or boredom, but in response to external (i.e., environmental) food cues, which drive eating in the obese until those cues are removed (or consumed). External food cues include the sight or smell of palatable food and other salient cues in the situation indicating that eating is appropriate. When external cues are absent, the obese are not motivated to eat, even if they are substantially food-deprived. This focus on internal and external cues is often seen as originating in Schachter’s earlier research on emotion, although a close reading reveals significant differences in Schachter’s analyses of these two domains.
Schachter’s obese-externality theory achieved widespread attention because it challenged long-standing ideas about the causes of obesity by means of several innovative and dramatic experiments. These experiments showed that obese people’s food intake is less affected by manipulations of food deprivation and distress than is that of normal-weight people. Obese individuals, for instance, are less disturbed by time-zone changes or by the requirements of religious fasting, as long as food cues are not prominent. These clever studies, written with great flair, were complemented by studies demonstrating that obese people are differentially affected by manipulations of external cues, ranging from varying the visual prominence of food cues (by, for example, altering the lighting or providing nuts either shelled or unshelled) to doctoring a clock (so that dinnertime arrived either early or late) to offering experimental subjects either one or three sandwiches to eat. These studies fascinated the research community, even if the data were not always robust.
Schachter’s research was correlational, showing that obesity is associated with externality. He assumed that externality (in an environment rife with food cues) causes obesity. But what is the source of externality? Schachter postulated that impairment of the brain’s ventromedial hypothalamus (VMH) was responsible; rats with VMH damage behaviorally resemble obese humans. This line of reasoning was extended by Schachter’s student Richard Nisbett (1972), who argued that suppression of VMH functioning was a consequence of weight suppression by dieting or other means, which is common among the obese. This proposal led in turn to research by C. Peter Herman and Janet Polivy (1980) on restrained eating (dieting), which hinged on the notion that even normal-weight people who suppress their weight ought to be especially external. Work on restrained eating, however, quickly turned away from questions of internal versus external. The Eating Disorders Inventory contains a scale concerned with interoception, the perception of one’s own internal states, which is weak in those with eating disorders; but again, the eating disorders literature pays scant attention to Schachter’s internal/external distinction.
Challenges to the obese-externality theory include the argument that internal and external cues reciprocally influence each other and are thus inseparable. Research shows that external cues (such as social influence and portion size) exert such a powerful influence on food intake in everyone that it is misleading to identify external responsiveness exclusively with the obese. Still, Schachter’s original proposal has not been disproved so much as superseded by subsequent formulations, all of which owe a debt to his groundbreaking demonstrations of how eating may be studied experimentally and creatively.
SEE ALSO Nutrition; Obesity; Overeating; Schachter, Stanley
BIBLIOGRAPHY
Herman, C. Peter, and Janet Polivy. 1980. Restrained Eating. In Obesity, ed. A. J. Stunkard, 208–225. Philadelphia: Saunders.
Nisbett, Richard E. 1972. Hunger, Obesity, and the Ventromedial Hypothalamus. Psychological Review 79: 433–453.
Schachter, Stanley. 1968. Obesity and Eating. Science 161: 751–756.
Schachter, Stanley. 1971. Some Extraordinary Facts about Obese Humans and Rats. American Psychologist 26: 129–144.
C. Peter Herman