People who fill up on tasty treats are more likely to return for seconds than those who eat food that's boring and bland, a new study found.

That may sound obvious, but Italian researchers used cookies, cakes and tiramisu to find out why the food we love keeps us coming back for more. The reason: a bit like addictive substances, the taste activates reward signals in the brain.

"Our preliminary findings show that when a normal-weight healthy subject's motivation to eat is generated by the availability of highly palatable food and not by food deprivation, a peripheral activation of two endogenous rewarding chemical signals is observed," the researchers wrote in a study set to be presented at the 94th annual Endocrine Society meeting in Houston.

The researchers tracked plasma levels of the hunger hormone ghrelin and the marijuana-like brain chemical 2-AG in study subjects who dined on delicious or, well, disappointing meals. Those who ate from the "palatable" plate had higher levels of both.

Dr. David Katz, director of the Yale University Prevention Research Center, said the study corroborates what most people already knew: Tasty food makes it hard to stop eating.

"We know that people overeat candy bars but not cauliflower; jelly beans but not pinto beans," he said. "We know that people still have room for dessert at the end of a large meal when they're otherwise too full for another bite."

The famous slogan, "Betcha can't eat just one," Katz said, is true.

More than one-third of American adults are obese, according to the U.S. Centers for Disease Control and Prevention. The major culprit: an imbalance between calories consumed through food and spent through exercise.

"Food should be a source of pleasure, but there should be sensible rules to bound that pleasure, or you are apt to get in trouble," said Katz. "Many things that are pleasurable are dangerous. Food is no exception."

Katz said to steer clear of tempting fare if you're already full.

"By all means, love food that loves you back. But don't go out of your way to expose yourself to the most tempting foods when you have already filled your belly," he said. "That's a formula for overindulgence."

Dr. Stephen Cook, a pediatrician at the University of Rochester Medical Center, said the study offers some important food for thought on the development of food preferences.

"It's significant because the basic science data is showing that pleasure centers of the brain that get activated by tobacco, drugs or other addictions are getting activated by foods," he said. "As a pediatrician, I think it allows us to provide more carefully worded advice about not introducing solid food and sweetened beverages too early in life."

ABC News' Samantha Meaney M.D. contributed to the story.