People using weight loss injections require continued support, researchers have warned, after a major study found they regain weight far more quickly than those following traditional diet-based approaches.
Researchers at the University of Oxford found that people taking medications such as semaglutide (Wegovy) and tirzepatide (Mounjaro) do lose weight while on treatment, but on average put it back on within 20 months of stopping the injections, reports RTE.
Any gains seen in blood sugar control, cholesterol and blood pressure are also lost once people discontinue the drugs, leaving patients back at their original starting point.
By comparison, people who lose weight through healthier eating and exercise, with appropriate support, tend to keep the weight off for much longer — just under four years — although they too generally regain it over time, reports RTE.
The findings come as separate research from University College London (UCL) and the University of Cambridge suggests people prescribed the newer weight loss drugs may be at risk of nutritional deficiencies and loss of muscle mass.
Currently, Wegovy can only be prescribed through the NHS for up to two years, while there is no such time limit for Mounjaro, reports RTE.
Most people using Wegovy and Mounjaro pay for them privately due to strict eligibility criteria for NHS access.
However, research indicates that around half of users stop taking weight loss medication, often because of the cost, side-effects, or because they feel they have reached their target weight, reports RTE.
The Oxford study, published in the British Medical Journal (BMJ), analysed 37 studies involving more than 9,000 participants.
The average treatment period was 10 months, with a mean follow-up of eight months, reports RTE.
People taking any form of weight loss drug lost an average of 8.3kg during treatment, but regained 4.8kg within the first year and returned to their starting weight within 1.7 years of stopping medication.
Those using Wegovy or Mounjaro specifically lost just under 15kg, but regained 10kg within a year of discontinuing treatment, reports RTE.
Based on projections from one year of data, they regained all of the lost weight within 1.5 years.
All cardiometabolic measures — including blood glucose and cholesterol — also returned to baseline levels around 1.4 years after stopping medication, reports RTE.
Susan Jebb, professor of diet and population health at the University of Oxford: “In summary, what we’ve shown in this particular piece of analysis is that weight regain after medication is common and is rapid,
“The cardiometabolic benefits essentially parallel weight – and so as weight is regained, the cardiometabolic benefits are lost, reports RTE.
“It’s important to note that the rate of weight regain is almost four times faster than after behavioural programmes, and that’s regardless of the amount of weight loss during treatment.”
She suggested that tackling obesity long-term may require a lifelong solution — whether ongoing use of obesity drugs, behavioural support, or a combination of both, reports RTE.
She said: “Obesity is a chronic relapsing condition, and I think one would expect that these treatments need to be continued for life, just in the same way as blood pressure medication,
“We should see this as a chronic treatment for a chronic condition, reports RTE.”
Prof Jebb said combining behavioural programmes focused on diet and exercise with drug treatment leads to greater weight loss.
“However, when the drug stops and appetite returns, it seems that those strategies are not sufficient to enable people to continue to manage their weight,” she said, reports RTE.
“In contrast, in behavioural programmes where people haven’t had the extra assistance of drugs, they probably have to practice those strategies more, and maybe they therefore are more persistent over time.”
She said it was “very clear that some type of treatment, some sort of intervention, needs to continue” if the long-term benefits of obesity drugs are to be maintained, reports RTE.
The expert added that while some people try tapering off medication or using intermittent treatment, and others rely on behavioural support, “the jury is out” on which approach works best.
Prof Jebb also warned that people paying privately for these medications “need to be aware of the very high risk of rapid weight regain when treatment ends” so they can make informed decisions about long-term use “aware of the financial consequences”, reports RTE.
Sam West, a study author and postdoctoral researcher at the University of Oxford, said: “People taking medication lose more weight compared with behaviour programmes, but they regain the weight four times faster.”
In the study, researchers also questioned whether drug treatment is cost-effective for the NHS, reports RTE.
They concluded: “As obesity is a chronic and relapsing condition, prolonged treatment with weight management medications may be required to sustain the health benefits,
“Further research is needed to study how to support people to use these drugs effectively, either through prolonged adherence or, possibly, through intermittent periods of treatment, reports RTE.”
Dr Adam Collins, associate professor of nutrition at the University of Surrey, said the research showed “weight regain is amplified when you cease taking these drugs”.
He added: “There are plausible explanations for why. The first relates to how these drugs (GLP-1 agonists) work. Artificially providing GLP-1 levels several times higher than normal over a long period may cause you to produce less of your own natural GLP-1, and may also make you less sensitive to its effects. No problem when taking the drugs, but as soon as you withdraw this GLP-1 ‘fix’, appetite is no longer kept in check, and overeating is far more likely. Like any addict, going cold turkey is a real challenge,” reports RTE.
Separate research published in *Obesity Reviews* found there is limited strong evidence on nutritional advice and support for people taking semaglutide and tirzepatide.
Dr Marie Spreckley, of the University of Cambridge, said: “Many people receive little or no structured guidance on diet quality, protein intake, or micronutrient adequacy while experiencing marked appetite suppression,” reports RTE.
“If nutritional care is not integrated alongside treatment, there’s a risk of replacing one set of health problems with another, through preventable nutritional deficiencies and largely avoidable loss of muscle mass,” reports RTE.
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