People are more likely to eat more the more food is in front of them.

Marion Nestle: Actually there’s very good research now that shows why people overeat.  It turns out that anybody, no matter how educated you are about it – even me – I will overeat if I’m presented with a large amount of food.  In fact you can demonstrate that the larger portion of the food presented to somebody, the more calories they will eat from that food even if they don’t finish it.  Food that is closer to you will be consumed in larger amounts than food that’s further away.  Food in wide, fat glasses will be consumed in greater number of calories than in tall, thin glasses.  I mean there are all kinds of sort of visual and little tricks that companies use to get people to eat more food.  They knew all of this.  We’ve only learned about it recently through the work of people doing terrific research.