There are three forms of obesity – but one responds much better to Mounjaro

There are three different forms of obesity, but one responds with much faster weight loss if people use slimming jabs like Mounjaro and Wegovy, a study suggests. Those in this so-called “super-responder” group lost twice as much weight as others in the first six months of using Mounjaro. Researchers believe the super-responders have naturally low levels of GLP-1, the gut hormone mimicked by Mounjaro and other jabs to suppress appetite and encourage weight loss. Professor Alexander Miras, an obesity researcher at Ulster University who wasn’t involved in the study. said: “If they are deficient in this hormone, then they do much better than people who don’t have this biology.” Hunger returns faster People vary in how much weight they lose in response, so Dr Andres Acosta, a gastroenterologist at Mayo Clinic in Minnesota, wondered if that was influenced by differences in their biology. His team carried out a range of tests on nearly 500 obese people, and 61 of them then started treatment with Mounjaro, so their response to the injections was tracked. The super-responders made up a quarter of the total group. Before starting Mounjaro, they had naturally low levels of GLP-1, as well as faster stomach emptying after meals. They also felt hungry more quickly after eating. A second group had moderate GLP-1 levels, and average rates of stomach emptying. A third group had high GLP-1 but fast stomach emptying. These differences were reflected in people’s response to Mounjaro: after six months on the jabs, the super-responders had lost 21.5 per cent of their weight, compared with 12 per cent for both other subtypes. Average weight loss with Mounjaro is usually 23 per cent after 18 months, after which weight plateaus. The drugs are meant to be taken long-term as weight returns if they are stopped. The super responders lost more weight when using Mounjaro (Photo: Matthew Horwood/Getty) Super response predicts final weight loss While this study only lasted six months, a faster initial weight loss from jabs usually means people will lose more weight in total, said Miras. Professor Naveed Sattar, a cardiometabolism specialist at the University of Glasgow, said the results helped explain differences in response to the medicines – but that most people lose a useful amount of weight from either Mounjaro or Wegovy, regardless of their obesity subtype. “The vast majority will benefit to some extent,” he said. Dr Nerys Astbury, a nutrition scientist at the University of Oxford, said the numbers of people included in the study were too small to draw firm conclusions, and that there may be more obesity subtypes. For instance, there could be differences in levels of other gut hormones, as well as external factors that affect weight. “There are differences in social and environmental exposures as well, and they’re all likely to interact to result in the overall risk,” she said. Sattar said that several new kinds of slimming drugs are likely to arrive in the next few years that work by mimicking different gut hormones. “People who don’t respond so well on one drug will either try a different drug which has got different targets, or we’ll add on another drug on top of a GLP-1 one,” he said. “That’s the direction of travel.” Weight loss resolution Weight loss has been revolutionised since the arrival of the Wegovy jab (also called semaglutide) in 2023, then Mounjaro (tirzepatide) two years later. The medicines are not widely available through the NHS, so in the UK, an estimated one to two million people are buying them from online pharmacies. Wegovy injections containing semaglutide are available through NHS specialist weight management services. Mounjaro jabs are available from GPs, but complex body mass index (BMI) restrictions are in place, prioritising only those with the highest clinic need. Wegovy recently launched its semaglutide tablet, causing a surge of new customers, the first pill to be approved in the UK. Superdrug Online Doctor is selling the 1.5mg starting dose of the Wegovy pill at £99 a month for existing patients. New patients can get the same dose for £79 a month. They will not be used on the NHS until they are approved by the National Institute for Health and Care Excellence (Nice). The study was published in the journal, Gastroenterology.