One of Australia’s leading nutrition experts has warned that the soaring use of weight-loss drugs could expose patients to serious nutritional deficiencies — and in rare cases scurvy — after new research found global clinical trials rarely assess whether users are eating adequately.
Clare Collins, professor of nutrition and dietetics at the University of Newcastle’s School of Health Sciences, said a major systematic review to be published on Tuesday revealed a significant gap in understanding the side effects of appetite-suppressing medicines known as GLP-1s.
While drugs such as Ozempic, Wegovy, Mounjaro and Saxenda are associated with substantial weight loss and improved blood-glucose control, Collins said there was little evidence on how they affect dietary intake and overall nutrition.
“In extreme cases, GPs are reporting incidents of scurvy,” Collins said, referring to a disease caused by severe vitamin C deficiency that was common among sailors between the 16th and 18th centuries. British pop star Robbie Williams disclosed last year that he developed scurvy after using weight-loss medication. Separate case reports have also identified thiamine deficiency, which can lead to neurological and cardiovascular complications.
“I’ve heard this anecdotally from GPs saying they’ve seen cases of scurvy,” Collins said. “Let’s not wait for every GP to encounter it. We need to be proactive and link chronic disease management plans to dietitian referrals.”
Collins stressed that weight loss alone should not be equated with good health. “A reduction in body weight does not automatically mean a person is well nourished or healthy,” she said. “Nutrition plays a critical role in health, and right now it’s largely missing from the evidence.”
The review, led by Collins and conducted by researchers at the Hunter Medical Research Institute and the University of Newcastle, analysed 41 randomised controlled trials involving more than 50,000 participants over the past 17 years. Only two of those studies measured or reported participants’ dietary intake.
“Only one trial had published what people actually ate,” Collins said. “We contacted all the authors and obtained data from one more study. This is a major blind spot. For medications of this cost and scale, it’s a significant omission.”
The findings come as the use of GLP-1 drugs accelerates globally and in Australia. Government data shows more than 400,000 Australians are currently using the weekly injections through the private market. The Albanese government is also considering expanding access under the Pharmaceutical Benefits Scheme, although eligibility would remain restricted to people with diabetes or severe obesity combined with cardiovascular disease.
Dietitians Australia chief executive Magriet Raxworthy said the nutritional implications of widespread GLP-1 use had been overshadowed by the focus on weight loss.
“These medicines significantly suppress appetite,” Raxworthy said. “Without personalised medical nutrition therapy from a dietitian, people may struggle to meet their nutritional needs and face risks including muscle loss, reduced bone density, micronutrient deficiencies and disordered eating behaviours.”
“Medication alone does not deliver sustainable health outcomes,” she added.
While some telehealth providers in Australia offer dietitian-led coaching as part of weight-loss drug packages, experts say the emphasis remains on reducing weight rather than ensuring adequate nutrition.
Collins said dietary support should be integrated into GP prescribing practices and called for further research into the long-term nutritional impacts of GLP-1 medications as their use continues to rise.
