These participants were compared to a control group of five overweight and obese people who weren't in the programme.
Both groups had MRI brain scans at the start of the study and again six months later.
Read: Diet & your brain: behaviour
The scans revealed that the people in the weight-loss programme had changes in areas of the brain reward centre involved in learning and addiction.
Specifically, this area showed increased sensitivity to healthy, low-calorie foods and decreased sensitivity to higher-calorie foods, according to the study published in the online journal Nutrition & Diabetes.
We don't start out loving junk food
"We don't start out in life loving French fries and hating, for example, whole wheat pasta," study senior author Susan Roberts, director of the Energy Metabolism Laboratory at the U.S. Department of Agriculture's Human Nutrition Research Centre on Ageing at Tufts University, said in a news release.
"This conditioning happens over time in response to eating (repeatedly) what is out there in the toxic food environment," explained Roberts, who is also a professor at the School of Nutrition Science and Policy at Tufts and an adjunct professor of psychiatry at the university's School of Medicine.
And, according to study first author Thilo Deckersbach, "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."
Deckersbach is a psychologist at Massachusetts General Hospital in Boston.
Read: Optimistic women make healthier food choices
"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," Deckersbach said in the news release.
Roberts pointed out that "there is much more research to be done here, involving many more participants, long-term follow-up and investigating more areas of the brain; but we are very encouraged that the weight-loss programme appears to change which foods are tempting to people."
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