New light shed on who benefits most from weight-loss jabs
A study published in the Nature journal reveals that individuals with certain genetic differences related to hunger and digestion may achieve more significant weight loss when using drugs such as Wegovy and Mounjaro. These findings could clarify why some people experience greater results while others encounter severe side effects, including nausea and vomiting.
Drug Mechanism and Genetic Insights
These medications work by mimicking a natural gut hormone, suppressing appetite and promoting a sense of fullness. Researchers analyzed genetic data from 15,000 participants who had previously enrolled in gene-testing programs through 23andMe. Their analysis linked specific genetic variations to the effectiveness of weight-loss treatments.
“The study identified a genetic variant connected to weight loss, which also correlates with nausea,” explained Professor Ruth Loos from the University of Copenhagen. “Individuals with this variant tend to lose more weight.”
According to the research, people carrying two copies of the gene can expect up to double the weight loss compared to those with one copy. The variant is prevalent in those of European descent, with 64% having one copy and 16% having two, while only 7% of African Americans carry a single copy.
Side Effects and Variability in Outcomes
The study also uncovered another genetic factor tied to intense side effects, particularly vomiting, when using tirzepatide (Mounjaro). This could mean up to 1% of users experience vomiting that is 15 times more severe than typical. Despite the genetic impact being modest, Prof Loos emphasized its importance in understanding weight-loss responses.
“Genetics is just one piece of a broader puzzle,” noted Dr Marie Spreckley from the University of Cambridge. “Behaviors, health conditions, and treatment details all play a role in determining outcomes.”
Additional factors, such as age, sex, and ethnicity, also influence results. Women, for instance, are more than twice as likely to lose 15% of their body weight on Mounjaro than men, though the reasons remain unclear.
Future of Weight-Loss Treatment
Combining genetic and clinical data might one day enable personalized treatment plans, a concept known as precision medicine. However, Professor Naveed Sattar from the University of Glasgow highlighted that current practices have not yet adopted these insights. “While these findings are scientifically intriguing, they are far from altering standard care,” he stated. “More rigorous trial data is essential to understand the risks and rewards of these therapies.”
Approximately 1.6 million people in the UK have used weight-loss drugs in the last year, with many purchasing them privately. The NHS provides Wegovy and Mounjaro to only a fraction of patients, typically those with severe obesity and related conditions. Weight loss percentages vary widely, ranging from 11.7% on average to as much as 30% in some cases, depending on individual responses and treatment factors.
