The study involved 50 overweight or obese adults, with a BMI of between 27 and 40, and an average weight of 95kg, who enrolled in a 10-week weight loss program using a very low energy diet.
Levels of appetite-regulating hormones were measured at baseline, at the end of the program and one year after initial weight loss.
Results showed that following initial weight loss of about 13 kgs, the levels of hormones that influence hunger changed in a way, which would be expected to increase appetite.
These changes were sustained for at least one year. Participants regained around 5kgs during the one-year period of study.
The study revealed the important roles that hormones play in regulating body weight, making dietary and behavioural change less likely to work in the long-term, said Professor Joseph Proietto from the University of Melbourne and Austin Health.
"Our study has provided clues as to why obese people who have lost weight often relapse. The relapse has a strong physiological basis and is not simply the result of the voluntary resumption of old habits," he said.he study was published in the New England Journal of Medicine.