People can train their brains to prefer healthy low-calorie foods over unhealthy higher-calorie foods, according to a recent study.

Researchers from Tufts University and Massachusetts General Hospital found that that it is possible to reverse the addictive power of unhealthy food while also increasing preference for healthy foods.

"We don't start out in life loving French fries and hating, for example, whole wheat pasta," Susan B. Roberts, senior and co-corresponding author of the study, said in a statement. "This conditioning happens over time in response to eating -- repeatedly!"

Scientists have suspected that, once unhealthy food addiction circuits are established, they may be hard or impossible to reverse, subjecting people who have gained weight to a lifetime of unhealthy food cravings and temptation.

For the study, Roberts and colleagues studied the reward system in thirteen 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.

Both groups underwent magnetic resonance imaging (MRI) brain scans at the beginning and end of a six-month period. Among those who participated in the weight loss program, the brain scans revealed changes in areas of the brain reward center associated with learning and addiction. After six months, this area had increased sensitivity to healthy, lower-calorie foods, indicating an increased reward and enjoyment of healthier food cues. The area also showed decreased sensitivity to the unhealthy higher-calorie foods.

"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, Ph.D., a scientist in the Energy Metabolism Laboratory at the USDA HNRCA 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 hypothesize that several features of the weight loss program were important, including behavior change education and high-fiber, low glycemic menu plans."

Researchers said there is much more research to be done on this subject.

"But we are very encouraged that, the weight loss program appears to change what foods are tempting to people," Roberts said.

The findings were recently published in the journal Nutrition & Diabetes.