Psychologists Peter Herman and Janet Polivy examined 30 years of research on eating habits. Herman said that people are often "rudderless" when confronted with food.
"Frequently, eating occurs within what we have termed a zone of biological indifference, in which the individual is neither genuinely hungry nor genuinely sated," he said. "Without any particular biological reason to start, continue or stop eating, we are particularly vulnerable to socially based influences."
They found, for example, that someone who might refuse a second helping at a formal dinner party will overeat at an all-you-can-eat buffet or while eating with family or close friends.
The study was published in Psychology & Behavior.