Brian Wansink does cool studies. Previous studies of his have looked at how a number of factors such as the size of your dinner plate can influence how much you eat (see: http://smallplatemovement.org/).
His latest cool study, which will soon be published in The International Journal of Obesity, examines how the size of the meals portrayed in paintings of the Last Supper have changed over the years – hundreds of years (see figure below). He found that since the year 1000 A.D., the relative size of bread and plates (compared to the sizes of the heads as a control measure) depicted in paintings of the Last Supper have increased by 23 and 66%, respectively.
Pretty cool study, huh? Sometimes a little creativity goes a long way.