Why Do People Eat Too Much? Jonah Lehrer

“It seems to me that our three basic needs, for food and security and love, are so mixed and mingled and entwined that we cannot straightly think of one without the others.”
- M.F.K. Fisher

Human beings are notoriously terrible at knowing when we’re no longer hungry. Instead of listening to our stomach – a very stretchy container – we rely on all sorts of external cues, from the circumference of the dinner plate to the dining habits of those around us. If the serving size is twice as large (and American serving sizes have grown 40 percent in the last 25 years), we’ll still polish it off. And then we’ll go have dessert.

Consider a clever study done by Brian Wansink, a professor of marketing at Cornell. He used a bottomless bowl of soup – there was a secret tube that kept on refilling the bowl with soup from below – to demonstrate that how much people eat is largely dependent on how much you give them. The group with the bottomless bowl ended up consuming nearly 70 percent more than the group with normal bowls. What’s worse, nobody even noticed that they’d just slurped far more soup than normal.

Or look at this study, done in 2006 by psychologists at the University of Pennsylvania. One day, they left out a bowl of chocolate M&M’s in an upscale apartment building. Next to the bowl was a small scoop. The following day, they refilled the bowl with M&M’s but placed a much larger scoop beside it. The result would not surprise anyone who has ever finished a Big Gulp soda or a supersized serving of McDonald’s fries: when the scoop size was increased, people took 66 percent more M&M’s. Of course, they could have taken just as many candies on the first day; they simply would have had to take a few more scoops. But just as larger serving sizes cause us to eat more, the larger scoop made the residents more gluttonous.

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