Programmes to help people lose weight through changes to their diet, exercise or both, are mainstays of weight management. Despite their widespread use, many people worry that after the programmes end they will regain the weight they lost – or more - removing the health benefits.
To understand the effects of this, the study brought together 249 studies including 60,000 adults who were overweight or living with obesity. They compared the half who joined programmes to lose weight through diet or exercise, or both, with the half who had no support (or less support than offered on these programmes). They assessed what happened to people’s weight after the programmes ended, and what this meant for their physical and mental health.
As expected, people lost weight during the programmes. There was a lot of variability, but, on average, people weighed 5kg less at the end of the programme than they did at the start. In most studies of weight loss programmes, people who don’t receive support (those in the “control group”) also lose weight - these are people who not only want to lose weight, but have volunteered to be in a study to help them lose weight, which means they are highly committed. For this reason, the study used these “control groups” as a way to test the effect of the programme itself. On average, people assigned to a programme lost 2kg more than people in the control groups.
People who had been assigned to a diet and exercise programme gradually regained weight when the programme ended. Typically, it took at least five years to regain the weight that was lost during the weight loss programme - few studies followed people for more than five years. Some studies stopped at a point where people still hadn’t regained all the weight they had lost.
Oxford is a subscribing member of The Conversation. Find out how you can write for The Conversation.