Scientists at the Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging (USDA HNRCA) at Tufts University and at Massachusetts General Hospital conducted brain scans of adult men and women.
They found that it is possible to reverse the addictive power of unhealthy foods while also increasing preference for healthy foods.
"We don't start out in life loving French fries and hating, for example, whole wheat pasta," said senior and co-corresponding author Susan B Roberts, director of the Energy Metabolism Laboratory at the USDA HNRCA.
"This conditioning happens over time in response to eating - repeatedly - what is out there in the toxic food environment," Roberts said.
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.
To find out whether the brain can be re-trained to support healthy food choices, 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 programme designed by Tufts University researchers and five who were in a control group and were not enrolled in the programme.
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 programme, the brain scans showed changes in areas of the brain reward centre 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 programme 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 USDA HNRCA.