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, we brought together 249 studies including 60,000 adults who were overweight or living with obesity. We 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). We 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, we use 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.
We showed that weight loss led to improvements in risk factors for heart disease, including high blood pressure, high cholesterol, blood glucose and type 2 diabetes. On average, these reductions were small, but translated across a population, would lead to significant reductions in disease.
Later, as weight was regained, these improvements ebbed away. But even five years, later some benefits were still apparent. There was some evidence that the chances of developing diabetes or having a heart problem were reduced. But most trials didn’t follow people for long enough to be certain. There is some evidence that short-term reduction in risk factors can lead to long-term reductions in disease incidence.
On average, people who went on diet and exercise programmes improved their quality of life, but around two years after the programme ended, their quality of life was similar to people who did not go on a programme.
Forty-seven studies also looked at the effect of these programmes on mental health. Overall, there was no evidence that these programmes made anxiety or depression worse, either during the programme or after it ended. There was some evidence that anxiety and depression might be improved, particularly in programmes that combined diet and exercise, rather than ones that focused on diet alone. We need more studies to be sure about these findings.
We also looked at whether anything made people more or less likely to regain weight. There was a lot of variation in how much weight was lost and how quickly weight was regained. On average, the more weight people lost through diet and exercise programmes, the quicker they regained it after the programme ended. However, this faster rate of weight regain did not wipe out the initial weight loss for at least five years.
Programmes that paid people to lose weight tended to lead to faster weight regain once the payments stopped than for people who did not receive any financial incentives. Programmes that continued to be available outside of the study were linked to less weight regain. This might be because people could keep attending the programme for as long as they wanted, or engage with it again when they started regaining weight. This included weight management programmes provided in the community.
In our review, we didn’t look at weight regain after using other weight loss methods, like medications. There is some evidence from individual studies that weight regain after weight-loss medication is stopped may be faster than after diet and exercise programmes.
Benefits still accrue, despite weight regain
Weight regain isn’t inevitable, but it is very common. Some people keep off most of the weight they lose in the long term, but it’s hard to predict who this will be. No one sets out on a weight loss attempt wanting to regain weight, but our genes and the environment we live in make it harder for some people to keep off weight than others.
Nonetheless, our findings provide some reassurance that taking part in a diet and exercise programme to lose weight can benefit people’s health – even if they put the weight back on. Increasingly, obesity is thought of as a chronic, relapsing condition – one that may need repeated periods of treatment to reduce health risks in the long term.
Jamie Hartmann-Boyce, Associate Professor and Director of Evidence-Based Healthcare DPhil Programme, University of Oxford; Paul Aveyard, Professor of Behavioural Medicine, University of Oxford, and Susan Jebb, Professor of Diet and Population Health, University of Oxford
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