10.07.2025

Cashing in on obesity crisis

Weight loss drugs feature regularly in the media. They work in the short term, but what about the long term? And what about the side effects? James Linney looks at the background and provides the answers

You may have read in the news last week that the weight loss injection, Mounjaro, has finally been made available to treat obesity on the NHS. The Independent, for example, announced: “Mounjaro weight loss jabs now available from GPs.”¹ Yet beyond the headlines, as I will discuss, the reality is quite different - in fact it will remain impossible for the majority of people to get this treatment from their GP for many years to come.

Mounjaro, or one of the other weight loss injections - a group of medications known as GLP-1s - has been a regular feature in the media over the past few years; in fact, I cannot think of any other type of medication that comes anywhere close to GLP‑1s, in terms of hitting the headlines. Here, I will consider their astonishing journey from a little-used fourth-line treatment for type 2 diabetes to the most talked about and profitable medications in the world.

GLP‑1 medications - or to give them their full name, glucagon-like peptide‑1 receptor agonists - despite the sudden media interest, have actually been around for decades. In a 1987 paper published in The Lancet, scientists first identified Glucagon-like peptide‑1 as a human intestinal hormone that stimulates insulin production in the pancreas and lowers blood sugar.² In the following years attempts were made to develop this hormone into a treatment for type 2 diabetes. A breakthrough came in the 1990s, when research on the saliva of Gila monsters³ led to the discovery of exendin‑4 - a molecule very similar to the human hormone, GLP‑1, but much more stable. This was the basis for the development of all the GLP‑1 medications now available to treat both type 2 diabetes and obesity.

Early versions

It was not until 2005 that the first GLP‑1 medication was approved. Exenatide (marketed as Byetta), started being used. As we have seen, it worked by stimulating the pancreas to produce more insulin, helping to transport ingested glucose into cells where it is needed. These early versions of GLP medications were not favoured, as they required multiple injections a day, but they paved the way for other GLP‑1 diabetes treatments, which were more convenient, once-daily or once-weekly injections. Soon there were multiple products on the market, such as dulaglutide (Trulicity), liraglutide (Victoza) and semaglutide (Ozempic).

In time, clinicians noticed that patients on these medications were losing significant weight. Further research revealed that GLP‑1s not only help regulate blood sugar, but also activate receptors in the gut and brain, making people feel fuller, slowing digestion and reducing food cravings. Excitement grew: had researchers stumbled onto a medical cure for obesity? For pharmaceutical companies, this was like hitting the jackpot. They quickly began tweaking and patenting versions of the drugs to market them specifically for weight loss.

Obesity is arguably the biggest global threat to health (excluding those resulting from potential environmental breakdown). Since 1990, global obesity rates have more than doubled and adolescent obesity has quadrupled. According to the World Health Organisation, in 2022 one in eight people globally were living with obesity.⁴ By 2050, over half of the world’s population is projected to be obese.⁵ Obesity is not only a disease in itself, but a major risk factor for others - type 2 diabetes, hypertension, heart disease, liver disease and cancer, to name a few.

Despite all the life-prolonging and life-improving medical advances of modern times, over the past 50 years there had been almost no scientifically proven advances in treating obesity until GLP‑1s. The best treatment we had was an old and drastic one: major surgery with a gastric bypass or sleeve gastrectomy.

This has not prevented global weight loss markets growing into a multi-billion-dollar industry, which continues to grow exponentially and is predicted to be worth over $400 billion by 2030.⁶ This industry is in the business of promoting treatments which have absolutely no proven long-term weight-loss benefits, and which can in fact often cause harm - equating to unregulated snake oil salesmanship, distracting us from dealing with the real problems. From meal replacement shakes to keto diets, to intermittent fasting, most of these ‘solutions’ fail in the long run, causing people to regain weight and feel demoralised.

It is important to emphasise - people with obesity are not to blame for their disease. Few other diseases are so often met with blame and stigma. People are told they lack the willpower to “eat less and move more”, which only adds harm to those already suffering. This attitude reflects a profound misunderstanding of what obesity is: a complex interplay between genetics and environment.

Genetics have not changed in the last 40 years - but the environment has. We now live in an obesogenic world. Industrial food production is dominated by a few multinational corporations, whose main goal is, of course, profit. As Chris van Tulleken outlines in his book, Ultra-processed people, modern food is designed to be addictive, easy to consume quickly, and engineered to override natural hunger signals.

Ultra-processing strips out nutrition in favour of hyper-palatable food, full of industrial chemicals, with soft textures that require little chewing. These products often masquerade as ‘natural’ or even healthy. The result is no accident - it has been manufactured.

Good treatment?

Let us turn back to the GLP‑1 medications then, to consider two questions: firstly, are they any good at treating obesity? Secondly, and more importantly, what are the chances they will meaningfully help to reverse the obesity trends?

The answer to the first question is essentially that, yes, they are pretty good treatments - used correctly, they have the potential to be a useful tool, alongside diet and lifestyle changes, to help people with obesity lose weight. Most trials have compared the GLP‑1 plus diet and exercise support to a placebo with diet and exercise. Of the older GLP‑1s, Liraglutide (Saxenda) resulted in 8% of body weight lost at 56 weeks, and Semaglutide (Wegovy) 14.8% at 68 weeks. Tirzepatide (Mounjaro) was associated with an even bigger, statistically significant reduction in body weight from baseline, compared with placebo, of about 20%.⁷ Keep in mind that even a 5%-10% weight loss can significantly improve health outcomes, so a 20% loss of body weight can be transformative.

But we do need to keep in mind that it is still relatively early days, so these studies are not involving huge numbers of people. The big question of how people will do in maintaining their weight loss in the long term (over many years) remains unanswered. Concerningly, a recent analysis of 11 studies of older and newer GLP‑1 weight-loss drugs by the University of Oxford found that most patients regained their lost weight 10 months after stopping their treatment, raising the possibility that to maintain their weight loss people may have to be on the medication for many years, if not life - great news for the drug companies.

GLP-1s can also commonly cause side effects. Most are mild and short-lived - nausea, diarrhoea, headaches - but rare, serious effects like pancreatitis and gallbladder disorders can occur.

The established evidence in favour of GLP-1s to promote weight loss has resulted in the National Institute for Health and Care Excellence (NICE) recommending the use of semaglutide (Wegovy) in the specialist NHS weight-loss service (Tier 3), alongside support for a reduced-calorie diet and increased physical activity, since back in 2023⁸, and Mounjaro since December 2024. Despite this, the availability of GLP-1s on the NHS has been very restricted and postcode-dependent. Some areas do not even have a specialist Tier 3 clinic, whilst those that do are so overwhelmed that waiting lists are often more than two years and they have had to stop accepting new referrals. The primary reason why GPs are not allowed to prescribe these medications to people who qualify (ie, if they have a BMI greater than 35 and an obesity-related complication) is due to cost - the medications were priced so high that paying for them would have risked bankrupting primary care.

Even since June, when NHS England decided to make Mounjaro available on the NHS, it is only made available to a tiny percentage of people - only people with a BMI above 40 and with four different specific co-morbidities will qualify in the first 12 months, and after that the plan is to very gradually make it available for more people over a 12-year period.

NHS demotion

This denial of treatment has meant that many thousands of people have sourced the medications through private providers and the fact that they could choose to do this was quite unusual.

No sooner had NICE recommended GLP‑1s for treating obesity in 2023, the Medicines and Healthcare products Regulatory Agency (MHRA) made the decision for them to be available to buy on a private prescription from registered pharmacies. Usually the MHRA would only sanction private prescriptions for medications where the safety and effectiveness were well established - for example, some antibiotics for mild infections, or oral contraceptives - which have been around for decades. But here, with GLP‑1s, we have a new treatment for obesity for which very little long-term effectiveness and safety data is available, yet it can be immediately issued on private prescription. This has meant there is very little in the way of monitoring a patient’s side effects or adverse events that would routinely happen for drugs prescribed on the NHS; in addition, pharmacies provide very little or no support with diet and lifestyle changes that should always go alongside taking them.

I am sure that here we have an example of big pharma lobbying overruling any monitoring or safety considerations - clearly there was simply too much money to be made to wait for the NHS to start providing them. The cost of GLP‑1s is very high - the price for Mounjaro, for example, is somewhere between £198 and £249 per month for the maintenance dose (15mg), meaning they are simply unaffordable for many people. Often they start buying the medication, get a good effect and start losing weight, but can only afford to do so for a limited amount of time. Then they regain lost weight, until they can afford it again at a later date, and so on.

Of course, none of this matters much to the pharmaceutical companies - as long as the sales keep rolling in, long-term health outcomes are irrelevant. And for the likes of Novo Nordisk and Eli Lilly, business is very good. Of the 10 most profitable medications globally in 2025, three (Ozempic, Wegovy and Mounjaro) are GLP-1s, which are forecast to equate to over $50 billion.

Desperate people are looking for cheaper, less regulated sources - fuelling a black market, with many buying them on social media or from unlicensed pharmacies online, putting them at risk of buying harmful, counterfeit injections or their inappropriate use - not to help promote the health of those with obesity, but as a cosmetic treatment to help people lose a bit of weight for their holiday.

Finally, turning to my second question - can GLP‑1s help slow down or reverse the rising obesity rates in the UK? Sadly, the answer must be no - it is very unlikely. Partly this is due to the way they are being denied to people who could benefit from them on the NHS - where they should be prescribed, alongside fully funded diet and lifestyle education and support from dietitians, psychologists and specialist doctors. The reality of the NHS funding and workforce crisis makes that currently impossible, and this is being fully exploited by pharmaceutical companies and private prescribers to make enormous profits.

More broadly, the global obesity crisis is a complex issue: its causes are more than people’s increasing appetites - and so GLP‑1s, although a potentially useful tool for an individual’s weight loss, will never be the answer in itself. The solution will have to come from a radical rethinking, not just of how food is produced, but an overcoming of the illogical and harmful essence of capitalism itself. A system that in its insatiable need to create new markets and accumulate profit has resulted in a food industry that insists on overconsumption of ultra-processed food and pharmaceutical companies driven not to improve health, but, first and foremost, to sell their products.