When I’ve been in the gym over the past few months, one of the things people like to talk about has nothing to do with fitness and building strength, and everything to do with weight loss. There’s a suspected culprit when celebrity after celebrity demonstrates a dramatic and sudden drop in size; one that made Danish pharmaceutical firm Novo Nordisk the most valuable company in Europe last year, and which Denmark has used as a bargaining chip as retaliation to the US when Trump announced his plans to take over Greenland.
Yes, it’s the widespread use of anti-obesity jabs (often referred to as GLP-1 drugs). In a 2024 poll, 12% of those surveyed in the US said they had taken or were taking them, with the numbers rising steeply year by year. This is roughly the same as estimates of antidepressant usage in the American population and far higher than the numbers taking heartburn medication. It’s become a coveted luxury in middle- and low-income countries, with high prices being the main barrier to usage – the cost is $95 a month in Brazil and $115 in South Africa, compared with about $350 in the US.
It’s not clear how many people are taking them in the UK: while prescriptions can be tracked, these are just part of the story of usage, given the growing online “hidden market”. This is where people hear about weight-loss drugs and find pharmacy or beauty websites to buy them from, with major risks to their health. Despite looking authentic, online purchases can be counterfeit and have quality issues.
One of my previous columns looked at how these drugs, called GLP-1 agonists, work. Right now, I’m more interested in what we’ve learned from usage over the past few years of widespread use. Surprisingly, as sales and awareness went up, there has been no published evaluation of their effectiveness on health outcomes and risks in the overall population. However, a recent study published in Nature Medicine sheds some light.
The authors went into the US Department of Veterans Affairs healthcare databases to identify individuals with diabetes who were on various types of treatments, including GLP-1 drugs. These almost 2 million people were followed, on average, for three and a half years to track the impact of drugs on 175 health outcomes. In those people taking GLP-1 drugs, there was reduced risk of substance use and psychotic disorders, seizures, Alzheimer’s disease and dementia, cardiometabolic disorders and several respiratory conditions.
On the flipside, there was increased risk of gastrointestinal disorders, pancreatitis, arthritic disorders, hypotension (very low blood pressure), fainting, kidney stones and kidney disease. GLP-1 drugs stimulate the pancreas to make insulin, but in doing so, can cause internal inflammation. And given their mechanism of triggering satiety and slowing digestion, GLP-1 drugs have been linked to nausea, vomiting, diarrhoea, constipation and more severe stomach disease.
A major limitation of the study was that the patients enrolled were largely older, mostly white males who received the drugs because of medical advice and to manage their diabetes. We don’t yet have a good longitudinal study on the health impacts for those taking the drug purely for weight loss, especially those within a healthy weight range already, which is linked to the uncertain data on the percentage of people acquiring the drug without a prescription – we simply don’t know much about the health and background of these people, or even how to identify and enrol them into a study.
What about for tackling obesity? In terms of their intervention as a public health tool, the expert view is mixed. One view is that this is an incredibly valuable tool for dealing with the chronic disease burden, and the main issue is accessibility and price. For example, University of Toronto professor emeritus Peter Singer has argued that widespread access globally could save almost a million lives a year for people with obesity and linked diseases. A different view is that we are simply ignoring the real drivers of obesity: cheap junk food, rubbish school meals and pricey nutritious food. I don’t think there’s a consensus among my colleagues yet, probably due to large uncertainty over the side effects and long-term risks of taking this medication, and awareness that prevention is better than cure.
Personally, I tend towards the precautionary principle – that is, when we don’t fully understand the potential benefits or costs of an intervention, we err on the side of caution. Obviously, if a doctor prescribes a GLP-1 drug as necessary, that’s a medical decision made on an individual basis. However, if you’re able to manage your weight with diet and exercise, the mental and physical health benefits are huge. It’s about strength, muscle mass, cardiovascular fitness and good nutrition. At a population level, otherwise healthy individuals going down the path of lifelong dependency on a medication with major side effects is concerning. But the draw of weight loss can be very powerful. Ironically, many of those – such as Elon Musk – who went back and forth on accepting the safety of Covid vaccines, seem super eager to get jabbed by GLP-1 drugs, damn any potential side effects. Ah yes, because Covid-19 vaccines were only about reduced risk of death, not losing weight.
Prof Devi Sridhar is chair of global public health at the University of Edinburgh, and the author of the How Not to Die (Too Soon)
