U of T psychology professors Peter Herman and Janet Polivy examined more than 30 years of research to survey the principles governing overeating and obesity. They found that while medical approaches continue to emphasize hunger and satiety as the root of the obesity epidemic, these two factors are usually not the most significant causes of overeating.
Instead, people allow environmental cues to dominate their eating choices, rather than adhering to selections that would satisfy their physical or nutritional needs. Portion size, palatability, variety and the food intake of fellow eaters are all potent influences on individual consumption. Norms may also become elevated depending on the social context in which they function, such as the case of the individual who, wishing to avoid appearing overindulgent, may refuse second helpings at a formal meal but accept them when eating at an all-you-can-eat buffet or among family and close friends.
"It's an insidious effect," Herman says. "People are often rudderless in eating situations and they look to the activity of others, their own previous behaviour or other social cues to guide them and thereby consume more than they need. Frequently, eating occurs within what we have termed a zone of biological indifference, in which the individual is neither genuinely hungry nor genuinely sated. Without any particular biological reason to start, continue or stop eating, we are particularly vulnerable to socially based influences."
"Norms of appropriateness have yet to achieve mainstream status in current medical research into obesity and overeating and in public policy concerned with curbing the obesity epidemic," Polivy says. "No one seems to be aware of the power that social influence has on eating, but if such considerations are integrated more deeply into this area, we may see some more practical results."
Professor Peter Herman
Department of Psychology
Professor Janet Polivy
U of T at Mississauga, Department of Psychology
U of T Public Affairs