If you're having a hard time putting down that pint of ice cream, it may not be because you're hard wired to keep eating it.
Recent research has suggested that eating junk foods, namely those edibles containing high amounts of fat, sugar and salt, can stimulate parts of the brain involved in seeking reward and pleasure. In other words, eating that pint of ice cream is addictive in the same way that nicotine or other drugs are addicting, the conclusion goes.
But that may not actually be the case, according to some experts.
"We are biologically wired to respond to certain tastes, textures and colors, but that doesn't mean it's an addiction," said Gabriel Harris, an assistant professor of food science at North Carolina State University in Raleigh.
In an influential study in 2010, scientists found that the brain circuitry of rats that ate unhealthy foods resembled the circuitry for rats exposed to drugs such as cocaine.
The study, published in the journal Nature Neuroscience, looked at three groups of rats over a period of 40 days. One group was fed regular rat food; another was allowed to eat high-fat human foods such as sausage, bacon and cheesecake for one hour each day, and members of the third group were allowed to eat as much high-fat food as they wanted.
The rats that stuffed themselves with unhealthy foods gained weight quickly.
When researchers applied electric shock to rats for eating unhealthy choices, the obese rats still preferred junk food regardless of the pain.
When researchers removed the junk food option and gave the rats a healthier diet, the obese rats refused to eat. Those rats starved themselves for two weeks after they were cut off from junk food.
But Harris cautioned that such behaviors do not mean the rats were addicted to the junk food.
"Abusing drugs doesn't affect brain chemistry in the same way," he said, "So making a general statement that foods affect the brain in the same way as drugs would be false."
Americans eat more junk food
There's no denying that Americans eat more junk food now than they did 20 years ago.
Between 2007 and 2010, U.S. adults consumed, on average, about 11 percent of their calories from fast food each day, according to a Centers for Disease Control and Prevention report released in February.
But does that mean people are addicted to these foods?
Not necessarily, said Joan Salge Blake, who teaches nutrition at Boston University and is a spokesperson for the Academy of Nutrition and Dietetics.
"Sweets and treats have been around forever," Blake said. "The problem isn't so much these foods, but the frequency that we allow them to be part of our diet."
She also noted that sweets and treats are cheap and available everywhere.
Although scientists are aware that certain ingredients do make foods tastier, clinical evidence doesn't prove there's a direct link with addiction, according to Harris.
"It's still something we don't know for sure," he said. "We have to collect more evidence."
Harris also said that it's a myth that all fast food has to be unhealthy.
"We need to change that definition," he said. "There are healthy 'fast foods' available, too. And more and more restaurants are offering healthy options."
The bottom line is that it may come down to personal choice.
"There are no bad foods, but there are bad diets," Harris said. "Consuming certain foods is fine as long as they are consumed in moderation and not all the time. To enjoy these things occasionally is reasonable. That's kind of balance we need to aim for."