More must be done to help people who have lost weight to keep the pounds off, experts have said.
Interventions that help people keep the weight off have "small but significant" benefits on weight loss maintenance, they said.
Academics from the University of Newcastle said in a bid to try and stem the UK's growing obesity epidemic, NHS officials should plough more resources into helping those who have managed to shed the pounds.
While weight loss interventions can produce initial weight loss, a third of people usually regain a third of the weight within a year and the rest within three to five years.
The academics, alongside researchers from Fuse, a centre for research in public health, examined previous studies on weight loss interventions.
Their paper, published in the BMJ, looked at 45 previous studies from around the world, involving 7,788 people. The interventions examined included helping with dietary changes, physical activity, drugs, food supplements and meal replacements.
They found that those who received weight loss interventions including both exercise and dietary changes regained 1.56kg less over a year than people who had no help to keep their weight off.
Dr Falko Sniehotta, reader in health psychology at Newcastle University, and member of Fuse, said: "Many people succeed in losing weight but struggle when it comes to keeping it off. If we are going to improve public heath then maintaining weight loss is one of the key issues that we need to solve.
"Our findings are encouraging as they demonstrate that we can slow down weight regain.
"As a society we make considerable personal and financial investments in weight loss. To translate these investments into better public health we need to ensure optimal support for those who have lost weight.
"More effort is needed to understand the psychology and physiology of weight loss maintenance, to optimise interventions and to make evidence-based support widely available to the people who have demonstrated their determination by losing pounds."