Imagine that you, a careful eater, go out for pizza with friends. Statistically speaking, here's what will happen, reports Brian Wansink, PhD, director of the Cornell Food and Brand Lab, in his book Mindless Eating: Why We Eat More Than We Think. Dining with just one friend, you'll eat about 35 percent more than when alone; with a group of four, about 75 percent more; and in groups of seven or more, 96 percent more. The reasons for overeating: spending a longer time at the table, mimicking our companions' pace often bite-for-bite, especially in the beginning of a meal) and defaulting to the group average.
The lesson: "Sit next to slow eaters," Wansink writes. "They can help you pace your eating, not the speed eaters who eat like they grew up in a family of 12."