Overweight children lose an average 2.6kg more than other children when they complete a specialised programme, figures have shown.
They also lose 4.3 cm on average from their waistlines, are fitter, take more regular exercise and have higher self-esteem after participating in the Mind, Exercise, Nutrition...Do It! (MEND) scheme.
The free after-school programme, which runs for nine weeks and is open to overweight children and their relatives, gives information about healthy eating, supermarket shops and exercise sessions.
The latest study, published in Obesity, used more than 100 children to compare the results of those using MEND and those in a control group.
Since it was established in 2004, more than 15,000 families have taken part in the scheme, which was created by Great Ormond Street Hospital and the University College London Institute of Child Health (ICH).
"These results suggest that the MEND programme helps overweight and obese children lose weight," said Professor Atul Singhal, head of clinical trials at the Childhood Nutrition Research Centre at ICH.
"They also show that child weight management programmes have a positive effect on a child's health and so could help to address the rising obesity problem in children."