If it sounds too good to be true, it probably is - so goes the old adage, warning against the temptations of miracle cures and easy fixes.

Yet miraculous new interventions - particularly in the world of medical science - can and do happen. From antibiotics to anaesthesia, over the past century pharmaceutical innovations have transformed healthcare and saved countless lives.

Even so, deciphering the exact capabilities of new treatments, and how these boundaries shape a process or product’s role within wider healthcare systems, is a complex but critical task.

Injections that help people to rapidly shed weight are the latest medical innovation to come under this type of scrutiny. For some, drugs like Mounjaro and Ozempic are the silver bullet doctors and policymakers have long been waiting for in the battle against rising obesity rates. For others, this type of treatment is yet another sticking plaster solution which fails to address the root cause of the issue.

A reasonable assessment probably places them somewhere in the middle. In which case, ramping up the use of GLP-1s agonists (often referred to as just GLP-1s) within the NHS could play an important role in bringing down obesity rates in the UK - even if they are no panacea.

What is evident is that these drugs are rapidly gaining popularity. NHS England prescriptions of GLP-1s - which cover only a small share of current usage, with most people accessing the jabs privately - have increased by almost 900% since Autumn 2020. Over the same period, prescriptions of Orlistat - a widely available older weight-loss medicine - have remained broadly stable.

While these figures are for individual prescriptions rather than total patients, they nonetheless tell a clear story: today, if people are using medication to lose weight, chances are they are taking some form of GLP-1.

How exactly does this type of medication help people living with obesity? What role should these jabs play within the wider health system? And what might the future of weight-loss treatment look like as pharmaceutical companies continue to develop these powerful new products?

To answer these questions, it is worth diving into the data and exploring GLP-1s in greater detail: what they do, and what they don’t do; who is taking them, and at what cost; and how might they fit into a wider set of measures to tackle obesity and help people live healthier lives.

In simple terms, GLP-1s trick your brain and body into feeling full. They do this by mimicking the actions of glucagon-like peptide-1 - a gut hormone produced naturally after a meal. Originally developed to help treat type 2 diabetes, the jabs also slow the rate at which the stomach empties, creating a feeling of fullness and curbing appetite. If you have a lower desire for food, you should find it easier to maintain a calorie deficit (ie, burn more energy than you consume) and lose weight

In England, the National Institute for Health and Care Excellence (NICE) currently recommends both semaglutide (sold as Ozempic or Wegovy) and tirzepatide (sold as Mounjaro). NICE recommends semaglutide for adults with a BMI over 30, with tirzepatide suggested for those with a BMI over 35 who are currently living with at least one weight-related comorbidity such as cardiovascular disease or hypertension.

Both treatments replicate the signal sent to both your brain and stomach after a meal: you have eaten enough and you don’t want any more. People using medications like Mounjaro and Ozempic report having lower appetites and experiencing less ‘food noise’ (distracting thoughts about food) throughout the day. By curbing people’s desire to eat, the drugs help patients consume fewer calories, making that all-important deficit easier to achieve and maintain.

Not only does the theory hold up in practice, but it may also be the case that the drugs alter the type of food people consume. Survey data from the United States shows that the majority of those taking GLP-1s report eating less calorie-dense and unhealthy foods like confectionery, fizzy drinks and baked goods.

While survey evidence like self-reported ‘food diaries’ are notoriously unreliable, this data does at least give us a rough picture of the desired effects of GLP-1s in action. Over half of those surveyed also reported eating more fruit and vegetables, and a little over 40% reported eating more ‘weight-loss management foods’ - things like protein bars/shakes as well as other low-fat products - while using GLP-1 medication.

However, it should be noted that this latter effect is not necessarily a direct result of the treatment. GLP-1s do not directly affect people’s food choices, and do not necessarily push people towards healthier options. There are other ways to achieve this, like changes in how food is made, promoted, and marketed to us (through mandatory nutritional standards in shops and restrictions on advertising of unhealthy foods).

Even so, GLP-1s are highly effective when it comes to weight loss. Tirzepatide users have been found to lose up to 21% of their body weight over 72 weeks, depending on the dosage. Similarly, research published in 2021 shows that people taking semaglutide lost around 15% body weight over 68 weeks of treatment on average. Over the same period, patients enrolled in ‘lifestyle only’ treatment programmes (eg, diet and exercise support) lost just 2.4% of their baseline body weight. For shedding pounds quickly, the jabs make a massive difference.

Of course, like many medications, GLP-1s are not without the potential for unpleasant side effects. The most common negative symptoms experienced by Ozempic and Wegovy users are nausea and vomiting, with about a third of users with type 2 diabetes quitting within six months, often as a result of these effects. More severe but much less common reactions include acute pancreatitis, kidney or gallbladder issues, and diabetic retinopathy (damage to the retina which can lead to sight loss).

Aside from these associated health risks, one of the main drawbacks of using GLP-1s for weight-loss treatment is the challenge of sustaining weight loss. According to a recent meta-analysis of 11 randomised trials involving people coming off GLP-1s, people start to regain weight as early as eight weeks after stopping treatment. Patients typically regain approximately two thirds of the weight they had lost within a year of stopping using the medication.

This rate of regain is much greater than that observed for patients who have gone through behavioural weight management programmes (although they tend to lose less weight in the first place). One systematic review of trials finds weight regain to be about 0.22kg per year for patients coming off weight management programmes, compared with 11.5kg within the first year for those stopping using semaglutide.

There are currently around 1.5 million people in the UK using GLP-1s. Of those, 95% are thought to be accessing the medication privately. Drugs like Mounjaro and Ozempic are not cheap: the average cost for a private user is about £150-200 per month.

Prices are also set to go up. Elly Lily - the US manufacturer of Mounjaro - announced in August that it plans to increase the cost of the jabs by 170% for UK consumers. This news led to a surge in demand, with people stockpiling doses ahead of the price hike. Asda Online Doctor experienced a 350% increas in Mounjaro orders following the announcement.

Climbing costs in the private market mean that for many people living with obesity or excess weight the only way to access GLP-1 medication is through the NHS. In 2024, NICE approved the use of tirzepatide as a weight-loss medication within the health service. The current plan is for a 12-year ‘cohort-based’ rollout, with those with higher clinical need treated first. This means that around 580,000 will be given the opportunity to get Mounjaro on the NHS over the next five years, with the longer-run goal to offer treatment to 3.4 million people.

A part of this headline figure could come from current private-sector users moving over to the NHS. It is not yet clear if we can say confidently that overall 580,000 more people will be using GLP-1s within five years. What does appear likely, however, is that the rapid growth of GLP-1 prescriptions (shown in Figure 1) is set to continue.

Nesta has modelled the effects of the proposed rollout. The first thing to note is that while the initial 580,000 figure looks impressive at first glance, this is just 1.3% of the total adult population of England. It also barely scratches the surface of the 13 million or so adults in England currently living with obesity.

The group set to benefit from the Mounjaro rollout are those living with class 3 obesity (defined as having a BMI over 40). In our model, around 400,000 people currently in this BMI class are assumed to take up the offer for treatment, with about 350,000 members of this group assumed to experience significant weight loss. Again, hold this figure up against the 13 million people in England with a BMI over 30 and the scale of the challenge looks daunting.

The current plan to roll out GLP-1s across the NHS is set to help a relatively small share of people. And remember, those who stop taking the medication are predicted to put back on two-thirds of the weight they lose within a year of ending treatment. This has led to worries among some regarding the risk of lifelong dependency on an expensive pharmaceutical product.

There are also concerns with the delivery of the rollout itself. The story so far reveals a series of teething issues. According to a freedom of information request made by the British Medical Journal, two months into the rollout and fewer than half of the commissioning bodies across England have begun prescribing Mounjaro. Of those who have started delivering the treatment, only nine out of England’s 42 integrated care boards (ICBs) have sufficient funding to support 70% of their eligible patients.

This has led to what critics are calling a ‘postcode lottery’ for GLP-1 access on the NHS. According to a recent investigation by The Guardian, the ICB for Coventry and Warwickshire has received funding to cover just 376 out of its 1,800 eligible patients during the first year of the rollout.

There are also potential issues regarding staff resources. According to current clinical guidelines, six hours of training is advised before healthcare professionals start prescribing GLP-1 medication. Patients should then be seen monthly and monitored for adverse effects as the dose is increased, then every six months over the longer run. Indeed, the current model of care proposed by NHS England for its Primary Care Weight Management service includes 21 GP visits, five psychologist sessions, five dietitian visits, four nurse consultations, three clinical pharmacist meetings, and one health-care assistant appointment per year. On top of this, in August 2025 NICE updated its guidance to recommend a year of structured support for people transitioning off GLP-1 medication. Meeting these requirements will come at a cost in terms of health care workers’ time.

Dialling down the level of supplementary support during treatment could help the health service scale up the rollout of GLP-1s more quickly. Indeed, the Tony Blair Institute has called the current care model ‘almost comically over-resourced’ and ‘hugely expensive’. But reductions to the limited post-treatment services for those coming off the medication risks tempering the long-run effectiveness of the jabs, if people quickly regain weight after stopping using the medication.

As the rollout continues and the BMI threshold is steadily lowered, the number of patients eligible for Mounjaro will also increase, requiring many extra appointments for the associated care (even though pharmacies are expected to play a significant part in delivering the 12-year programme). Given the current pressures on the UK health system and the state of the NHS waiting list, it may be difficult for individual ICBs to carve out the necessary capacity across their trusts to deliver this plan.

It is also worth noting that currently there is no statutory requirement for ICBs to offer GLP-1s for weight-management treatment. There are also several technical hurdles that policymakers must overcome if the rollout is to succeed, including the antiquated way that boards refer patients to specialist services as well as gaps in how the NHS Digital Weight Management Programme is connected to GP services. Addressing these challenges is vital if the proposed rollout is to work effectively.

Clearly, GLP-1s have the potential to improve individual people’s health by helping them lose weight quickly. Assuming they are indeed able to access the jabs - through the NHS or otherwise - people who use this type of weight-loss medication can experience life-changing results.

But the expansion of GLP-1 delivery is not the only lever policymakers have at their disposal for lowering obesity prevalence in the UK. From changing the food environment by regulating retailers and restaurants to taxing unhealthy food and drink products, there are various tools that the government can use to move the dial on this issue.

The key question centres on the relative costs and benefits of these different measures, as well as their headline effect on population-level obesity rates.

To explore these factors, researchers at Nesta developed the blueprint to halve obesity in the UK. This tool, which is updated regularly with new data and policy proposals, provides an interface that evaluates the effects of a wide range of obesity-reduction initiatives, including GLP-1 medications.

Using the toolkit, we can compare the costs and impacts (both monetary and in terms of obesity prevalence) of clinical interventions like weight-loss drugs with other measures such as the implementation of a healthy food standard for supermarkets.

On their own, GLP-1s are a highly effective but extremely costly policy choice. Extending access to semaglutide (eg, Ozempic or Wegovy) for 3 million people with a BMI over 30 could reduce obesity prevalence in the UK by as much as 41%. However, this would cost governments £42 billion over five years - equivalent to about 20% of the annual budget for the Department of Health and Social Care.

Using GLP-1s in tandem with other non-clinical measures is an attractive ‘hybrid’ approach. In the toolkit, we set out a ‘prevention and treatment' policy package which includes a treatment component (in the form of extra ring-fenced funding to provide GLP-1s on the NHS), as well as preventative measures like restrictions on advertising and promotions for high fat, sugar or salt (HFSS) foods and requiring supermarkets to meet a minimum ‘healthy food standard’.

The idea here is to offer those in need an effective treatment for losing weight, while also changing the food environment so that healthier options become the default. Crucially, this hybrid approach does not place extra burden on individual people to spend more or act differently in order to shed weight. It also makes sense to try to improve the healthiness of our food in general, so that fewer people ultimately end up in the cohorts that need clinical or pharmaceutical interventions.

According to our analysis, this package of seven complementary measures is high-impact and relatively low-cost. If implemented, this approach could reduce the number of people in the UK living with obesity by approximately 9 million at a cost of around £2.6 billion over five years, generating an estimated £32 billion in benefits to society.

The technological innovation at the heart of branded medication like Mounjaro and Ozempic is currently under patent. This means that a small number of private companies - including Eli Lilly in the United States and Novo Nordisk in Denmark - have a tight grip on prices, both for private users and public procurers like the NHS.

However, patents will eventually expire. This could could unleash a flood of 'generics' - cheaper versions of the medicines developed to the same specification as pre-existing ‘branded’ options. This could, in turn, widen access to weight-loss drugs around the world.

Here in the UK, the cost of GLP-1 medications are expected to plummet as patents for frontrunner products expire over the next decade or so. It seems likely that this will allow a greater number of UK patients to start using weight-loss drugs (either privately or via the NHS). The further development of oral alternatives could expand usage further, with those currently hesitant to inject themselves soon able to swallow a pill instead. This could also bring transport and storage costs down, further lowering prices.

While encouraging, this won’t change the fundamental limitations of GLP-1 weight-loss treatment. Without wraparound care (especially for those coming off the drugs), as well as changes to the wider food environment, it will remain difficult for people to maintain weight loss.

With this in mind, the government’s commitment to a healthy food standard - which includes health targets for supermarkets - is an encouraging step in the right direction. So too is the proposed rollout of Mounjaro for those most in need, providing the government quickly gets on top of issues regarding geographic inequality of access and offers appropriate support for those taking and coming off GLP-1 medication. What is clear is that prevention must remain at the core of obesity management.

In drugs like Mounjaro and Ozempic, the government has a powerful new tool at its disposal in the struggle against rising obesity prevalence. However, limiting factors like price, availability, and the risk of weight regain mean that GLP-1 treatment is not sufficient to tackle obesity on its own. Any rollout of weight-loss medication should be augmented with other health policies like wraparound care and changes to the food environment. GLP-1s have an important role to play, but they cannot be the only answer.