Hidden ingredient in weight loss pills may have 'adverse effects' linked to liver, scientists warn

This represents the first systematic in vivo investigation into how repeated SNAC exposure influences gut bacteria, metabolic processes and associated health indicators.

The findings point to potential biological consequences that warrant closer examination as pill-based obesity treatments gain wider adoption globally.

Conducting their research over a 21-day period using animal subjects, the Adelaide team documented several changes.

Beneficial bacteria responsible for breaking down dietary fibre declined noticeably, while short-chain fatty acids that protect the gut lining and regulate inflammation dropped.

Blood samples revealed heightened inflammatory markers, and liver weight increased - potentially indicating low-grade inflammation.

The cecum, where gut bacteria process fibre and generate protective compounds, was found to be smaller than expected.

Researchers observed a marked reduction in a brain-derived protein linked to cognitive function, though stress that these observations do not constitute proof of harm.

Semaglutide, the active ingredient in these widely prescribed medications, enters the bloodstream directly when administered via injection.

The tablet form, however, requires SNAC to protect it from stomach enzymes and facilitate absorption - without this compound, oral semaglutide would prove ineffective.

The United States granted approval for a pill version of Wegovy late last year, a development likely to increase daily SNAC exposure substantially as patients opt for the convenience of tablets over injections.

Obesity affects approximately 890 million adults and 160 million children worldwide — roughly one in eight people globally.

Prescriptions for these medications have risen sharply in recent years.

Lead author Amin Ariaee, a PhD candidate at Adelaide University, acknowledged the effectiveness of these treatments whilst calling for greater scrutiny.

"Obesity is a complex, chronic disease with serious health consequences. These medicines are highly effective and are helping many people," Ariaee said.

"But as oral versions become more widely used, we need to understand what repeated, long-term exposure to all ingredients in the pill means for the body - not just the active drug."

Senior Research Fellow Dr Paul Joyce urged caution in interpreting the results.

"Importantly, our findings do not prove that SNAC causes harm in humans," he explained. "However, they do show that the ingredient enabling these tablets to work may have adverse biological effects beyond drug absorption."