Researchers have found that:

• Some people have genetic variations that make GLP‑1 signaling less effective.

• Differences in the gut microbiome may influence how strongly the drugs suppress appetite.

• People with long‑term obesity may have brain‑reward pathways that are harder to shift.

• Lifestyle factors — sleep, stress, diet — can change how well the medication works.

The big takeaway: If someone doesn’t lose weight on a GLP‑1 drug, it’s not a personal failure — it’s biology. Future treatments may be more personalized, targeting multiple hormones or metabolic pathways to help more people respond.

Scientific American. (2025). Why Ozempic and Wegovy don’t cause weight loss for everyone

https://www.scientificamerican.com/article/why-ozempic-and-wegovy-dont-cause-weight-loss-for-everyone/

Not everyone loses weight on Ozempic or Wegovy — and scientists are finally uncovering why. These medications work by mimicking GLP‑1, a hormone that reduces appetite and helps regulate blood sugar. But people respond very differently because of genetics, gut biology, metabolism, and brain chemistry.

Why Ozempic and Wegovy don't cause weight loss in everyone.