Weight-loss injections, like Wegovy and Mounjaro, have been hailed as gamechangers. In clinical trials, people lost an average of 15%-20% of their body weight – results that seemed almost miraculous compared to traditional diet and exercise programmes.
Today, one in 50 people in the UK are using these treatments. Most of them – around 90% – are paying privately, at a cost of £120-£250 per month. But there’s a catch: more than half of people stop taking the drugs within a year, with cost being the main reason.
Our latest research reveals what happens next, and it’s sobering. On average, in clinical trials, people regain all the weight they lost within just 18 months of stopping the medication.
That’s surprisingly quick – almost four times faster than the weight regain seen after stopping weight-loss programmes based on diet and physical activity. The health improvements vanish too, with blood pressure, cholesterol and blood sugar levels returning to where they started.
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This matters because it means these drugs may need to be taken long-term – potentially for life – to maintain the benefits. Some private providers offer intensive support alongside the medication, and our review showed this helped people lose on average an extra 4.6kg. But there was no evidence that support during or after stopping the drugs helped to slow weight regain.
The rapid rebound raises serious questions about fairness and whether these treatments represent good value for the NHS. Obesity is far more common among people living in deprived areas, who are also least able to afford private treatment. NHS access is crucial to ensuring everyone gets equal care, regardless of their income.
The NHS is gradually rolling out these medications, but only to people with severe obesity (BMI over 40) and four obesity-related conditions, such as high blood pressure. That means many people who could benefit are effectively excluded unless they can pay privately.
Costs may eventually fall as existing drug patents expire and cheaper oral versions are developed, but that could take years. In the meantime, we need to make sure NHS access to these medications delivers the best possible value so more people can benefit.
Cost v benefits
The National Institute for Health and Care Excellence approved these drugs for NHS use because it judged them cost-effective by its usual standards. But those calculations assumed treatment would last two years, with weight being regained after three years of stopping. Our data shows that if treatment ends, weight comes back surprisingly quickly.
We also found that the improvements in things like blood pressure and cholesterol – the main reasons the NHS treats obesity – disappeared within the same timescale. This means the treatments may need to be continued long term to achieve lasting weight loss and health benefits, which completely changes the cost calculations.
More research is needed to estimate how cost-effective these medications really are, outside carefully controlled clinical trials, and for the actual patients being treated.
For people with obesity who don’t yet qualify for the medication based on the strict NHS criteria, the medication may not be cost-effective for widespread NHS use until the price drops substantially.
For this population, traditional weight management programmes remain the foundation of obesity treatment. Total diet replacement programmes, during which people eat nutritionally balanced soups and shakes instead of regular food for eight to 12 weeks, can achieve similar weight loss to the medications at a fraction of the cost.
Group-based weight-loss programmes, such as WW and Slimming World, achieve smaller average weight losses but can be cost-effective and even save the NHS money.
The new weight-loss medications have shown just how desperately people want help to lose weight. But the question of value for money remains unclear. Making cheaper weight-loss programmes available to anyone with obesity who wants support would allow fairer access to treatment and improve public health, though individual results are likely to be less dramatic than what could be achieved with long-term medication.
