New light shed on who benefits most from weight-loss jabs
A recent study published in the Nature journal has revealed insights into why certain individuals experience greater weight loss from drugs like Wegovy and Mounjaro. Researchers found that people with specific genetic variations related to appetite regulation and digestion may see more significant results when using these medications.
These drugs function by mimicking a natural gut hormone, which suppresses hunger and promotes a feeling of satiety. However, the study suggests that genetic differences play a role in determining how effective these treatments are for individuals. While the impact of genes is not the sole factor, it could explain why some people achieve substantial weight loss while others gain little or none.
Genetic Insights and Side Effects
By analyzing genetic data from 15,000 participants who had previously used 23andMe for testing, scientists identified a pattern linking certain variants to drug effectiveness. Professor Ruth Loos, from the University of Copenhagen, noted that one variant was associated with both increased weight loss and nausea. Those carrying two copies of the gene saw double the average reduction in body weight, approximately 0.76kg (1.6 lbs), compared to individuals with one copy.
“The study found a genetic variant associated with weight loss, which was also linked to nausea. People who have this variant tend to lose more weight,” said Prof Loos. She added that the variant is more common among individuals of European descent—64% carry one copy, while 16% have two. In contrast, only 7% of African Americans were found to possess a single copy of the gene.
The research also uncovered another genetic factor tied to severe side effects. For tirzepatide (Mounjaro), some users with specific variants may experience vomiting up to 15 times more intense than typical, affecting up to 1% of patients.
Broader Considerations
Dr Marie Spreckley from the University of Cambridge emphasized that genetics is just one piece of the puzzle. “Outcomes are influenced by behavioural, clinical, and treatment-related factors,” she explained. This includes exercise habits, dietary choices, and support systems, alongside existing health conditions.
Other variables, such as sex, age, and ethnicity, also appear to affect results. Women, for instance, are more than twice as likely as men to lose 15% of their body weight on Mounjaro. Similarly, younger individuals, as well as those of white or Asian backgrounds, may experience greater weight loss, though the reasons remain unclear.
Professor Naveed Sattar, a metabolic health expert at the University of Glasgow, highlighted that while these findings are scientifically intriguing, they are not yet sufficient to alter clinical practices. “We need more robust trial data to better understand the trade-offs between benefits and risks,” he stated, noting that precision medicine could one day use genetic and personal data to personalize weight-loss treatment options.
Approximately 1.6 million people in the UK have attempted weight-loss drugs in the last year, with most purchasing them through private online pharmacies. The NHS currently provides Wegovy and Mounjaro to a smaller group, typically those with severe obesity and related health conditions.
