A weekly dose of a diabetes drug appears to lead to significant weight loss in people with obesity, in a development experts have hailed as gamechanging. Obesity causes 1.2 million deaths in Europe each year, according to the World Health Organization, and the UK has one of the worst obesity rates. Efforts to tackle the disease have long been focused on diet and exercise, but many people who lose weight this way find they regain it over time. Now researchers say a diabetes drug, used alongside such interventions, can help people with obesity. Participants in a 72-week trial lost as much as 20% of their body weight. Writing in the New England Journal of Medicine, an international team report that they randomly split 2,539 overweight or obese participants into four equal groups. One group was offered a self-administered placebo injection once a week for 72 weeks, while the other three groups were offered either 5mg, 10mg or 15mg of a drug called tirzepatide. All participants were also given regular lifestyle counselling sessions to help them stick to low-calorie meals and at least 150 minutes of physical activity a week. On average, participants had a body weight of 104.8kg, or 16.5 stone, with 94.5% deemed obese. The majority were white and female, and none had diabetes. The results from those who stuck to the assigned intervention – almost 82% of the sample – reveal that at the end of the 72-week period participants given 5mg of tirzepatide each week lost an average of 16.1kg, those given 10mg lost an average of 22.2kg and those given the 15mg an average of 23.6kg. Those given a placebo injection lost an average of 2.4kg. The team add that among those assigned the highest dose of tirzepatide, 91% of participants lost 5% or more of their body weight, compared with 35% of those assigned the placebo. Fifty-seven per cent of those assigned the highest dose lost 20% or more of their body weight compared with 3% of those assigned the placebo. “We should treat obesity as we treat any chronic disease – with effective and safe approaches which target underlying disease mechanisms – and these results underscore that tirzepatide may be doing just that,” said Dr Ania Jastreboff of Yale University, the lead author of the research, which was presented during the American Diabetes Association 82nd Scientific Sessions. The study comes after the UK’s National Institute for Health and Care Excellence (Nice) approved the use of another drug, semaglutide, for certain groups of people with obesity in February. Prof Rachel Batterham, an obesity expert at University College London who was not involved in the work, said that like semaglutide, tirzepatide worked by mimicking hormones in the body that help people feel full after eating and which are often at low levels in people with obesity. While semaglutide mimics just one hormone, however, tirzepatide mimics two, potentially explaining why the latter appears to have a greater effect. “Weight loss is about improving a person’s health. If you want to improve the really difficult complications of obesity, then you need 15-20% weight loss. If you want to improve somebody’s heart failure or get rid of their obstructive sleep apnoea, reduce their risk of dying from cardiovascular disease, then we need much greater weight loss that we can achieve and sustain with diet alone,” Batterham said. Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London said higher doses of tirzepatide led to more weight loss, but they caused more side effects, mainly nausea, vomiting and diarrhoea, while a major concern with this class of drug were its effects on the pancreas. “This class of drugs only works providing the participants stick to the reduced calorie diet prescribed with the drug so it is not a magic bullet,” he said. Dr Simon Cork, a senior lecturer in physiology at Anglia Ruskin University, also said there were challenges. “These drugs are gamechanging for the obesity field but they will only work for as long as the drug is being taken,” he said. “Current guidance to Nice regarding semaglutide is to take the drug for a maximum of two years, after which it won’t be offered again. We know that this is very likely to result in a reversal of the weight loss effects for many people, the same is likely true for tirzepatide.” Naveed Sattar, a professor of metabolic medicine at the University of Glasgow, who was not involved in the work, said the latest findings were good news. He said, however, that like semaglutide, tirezpatide would be expensive for many years and its use would initially be restricted. “The emergence of these new drugs does not mean people should ditch lifestyles as it is far better to prevent obesity in the first place than treat it at a late stage when a lot of damage has already been done,” he said. “Fortunately, methods to help people improve their diet are evolving as we learn what works better. But of course, improving the food environment would have the biggest impact of all so should remain a focus for the government.”