Training yourself to prefer healthy foods over unhealthier, often high-calorie fare, takes commitment, but is managable, says new research from the Jean Mayer USDA Human Nutrition Research Center on Aging.

In a study published online in the journal Nutrition & Diabetes, a team from the research center, which is located at Tufts University and at Massachusetts General Hospital, has conducted brain scans of adult men and women revealing it's possible to reverse the addictive power of unhealthy eats while building a desire for healthy foods.

"We don't start out in life loving French fries and hating, for example, whole wheat pasta," the study's senior and co-corresponding author Susan B. Roberts, director of the Energy Metabolism Laboratory at the research center, said in a news release. "This conditioning happens over time in response to eating -- repeatedly! -- what is out there in the toxic food environment."

Scientists have long suspected once unhealthy food addiction circuits are established in the brain, they may be extremely difficult, if not impossible, to reverse -- subjecting people to lifetimes of unhealthy food cravings and temptation.

So, Roberts and fellow researchers studied the reward system in 13 overweight and obese men and women -- eight of whom were participants in a new weight loss program designed by Tufts University researchers and five who were in a control group and were not enrolled in the program.

At the beginning and again the end of a six-month study period, both groups underwent magnetic resonance imaging, or MRI, brain scans which, among the ones enrolled in the weight-loss program, showed changes in areas of the brain reward center associated with learning and addiction.

After the six months, the reward area had increased sensitivity to healthy, lower-calorie foods, indicating a greater sense of reward and enjoyment triggered by healthier foods, but a decreased sensitivity to the unhealthier selections.

"The weight loss program is specifically designed to change how people react to different foods, and our study shows those who participated in it had an increased desire for healthier foods along with a decreased preference for unhealthy foods, the combined effects of which are probably critical for sustainable weight control," said co-author Sai Krupa Das, a scientist in the Energy Metabolism Laboratory at the research center and an assistant professor at the Friedman School. "To the best of our knowledge this is the first demonstration of this important switch."

The authors of the study suspect several features of the weight loss program were important to the re-training process, including behavior change education and high-fiber, low glycemic menu plans.

"Although other studies have shown that surgical procedures like gastric bypass surgery can decrease how much people enjoy food generally, this is not very satisfactory because it takes away food enjoyment generally rather than making healthier foods more appealing," said first author and co-corresponding author Thilo Deckersbach, a psychologist at Massachusetts General Hospital. "We show here that it is possible to shift preferences from unhealthy food to healthy food without surgery, and that MRI is an important technique for exploring the brain's role in food cues."

Roberts summed up the findings by suggesting it's necessary to conduct more research, "involving many more participants, long-term follow-up and investigating more areas of the brain ... but we are very encouraged that the weight loss program appears to change what foods are tempting to people."