The researcher has set up several food experiments that show that the more people are given, the more they will eat, regardless of whether they are full or think the food tastes good.
Wansink says "in the obesity war, portion size is the first casualty.''
His experiments have included tomato soup, popcorn and potato chips. They target the visual clues people use to tell them it's time to stop eating.
In the soup experiment, some bowls are rigged with hidden tubes that keep them full, while others are not. Over two years of the experiment, students with bottomless bowls tended to eat 40 percent more than test subjects with regular bowls.