Brian Wansink, a professor of marketing and nutritional science at the University of Illinois at Urbana-Champaign, said how food is displayed and its variety of colors can lead people to overindulge and unknowingly bulk up.
His discoveries are summarized in the latest issue of the Journal of Consumer Research.
For example, adults offered six colored flavors of jellybeans mixed together in the same bowl ate 69 percent more than when the colors were each placed in separate bowls.
His work resembles work done by a Pennsylvania researcher.
Wansink and Barbar E. Kahn, of the University of Pennsylvania, found that moviegoers given M&Ms in 10 colors ate 43 percent more than those offered the same number of M&Ms in seven colors.
"People eat with their eyes, and their eyes trick their stomachs," Wansink said in an interview. "If we think there's more variety in a candy dish or on a buffet table, we will eat more. The more colors we see, the more we eat."