People who carry variations in two genes linked to appetite and digestion can lose more weight when taking drugs such as Wegovy and Mounjaro to treat obesity, research suggests.
The findings, outlined in the Nature journal, could explain why some people lose far more weight than others and why some have particularly bad side-effects, such as nausea and vomiting, while taking them.
The popular medicines remove feelings of hunger by acting like a natural gut hormone that makes users feel full.
While genes may play a relatively modest role in influencing how well these drugs work, experts say other factors as your sex, age, and even where you come from can also have an impact.
It is thought at least 1.6 million people in the UK have tried weight-loss drugs in the past year, and that number is expected to rise.
