GLP-1 weight-loss drugs like Wegovy and Zepbound have transformed obesity treatment, but about 10 percent of users are 'non-responders' who lose minimal weight despite months of treatment. Jessica Layeux's experience exemplifies this frustration - after 15 months on Zepbound, she lost only one or two pounds while spending thousands of dollars. The phenomenon has left many patients feeling defeated and questioning whether they're somehow at fault.

Scientists are investigating why some people see dramatic results while others see none. Genetic factors appear to play a role, with researchers at the University of Cambridge finding that variations in genes affecting hunger, fullness, and metabolism may predict drug response. Dr. Beverly Tchang from Weill Cornell Medicine notes that targeting just two hormones in the 'alphabet soup' of weight-regulating chemicals may explain limited effectiveness for some patients. Men appear more likely than women to be non-responders, possibly due to hormonal differences.

Research is advancing on predicting who will respond to which drugs. A Mayo Clinic study found genetic differences between GLP-1 responders and non-responders, with non-responders losing significant weight on alternative medications like phentermine-topiramate. Companies like Phenomix Sciences are developing genetic tests to guide treatment selection, though these haven't proven effective in independent trials. Meanwhile, pharmaceutical companies are developing new drugs targeting additional hormones, offering hope that non-responders may soon have more effective options.