A major Australian study has found that while testosterone treatment may help older men build strength and reduce body fat, it is unlikely to prevent type 2 diabetes on its own.
Researchers from the University of Adelaide led a national collaborative trial involving centres in Sydney, Melbourne, Perth and Brisbane to investigate whether testosterone therapy could help reduce the risk of type 2 diabetes in men aged 50 to 74 who were considered at high risk of developing the disease.
The latest findings come from a four-year study that followed earlier research involving more than 1,000 men. That initial trial found that testosterone treatment, when combined with a healthy lifestyle program, reduced the risk of developing type 2 diabetes by 40 per cent over two years compared with a placebo.
To determine whether testosterone alone could provide long-term protection, 120 men continued in the study for a further two years, receiving either testosterone treatment or a placebo without the lifestyle intervention.
The results showed testosterone therapy helped reduce body fat, increase muscle mass and strength, improve blood glucose levels and boost sexual desire. However, while many of these benefits appeared early and were maintained throughout the study, the positive effects on blood sugar control gradually declined over time.
Professor Gary Wittert, Director of the Freemasons Centre for Men’s Health and Wellbeing at the University of Adelaide, said the findings highlight the importance of healthy living in diabetes prevention.
“Some older men continued to experience small benefits from testosterone treatment for up to four years,” Professor Wittert said.
“However, the benefits for blood sugar control were strongest in the early stages of treatment. By the four-year mark, the proportion of men who had developed diabetes in the testosterone group was similar to those receiving the placebo.”
Researchers believe the findings reinforce the message that testosterone treatment should not be seen as a substitute for lifestyle changes.
“The most likely explanation is that testosterone is not a replacement for a healthy lifestyle and would need to be combined with a weight-loss program for the best chance of preventing type 2 diabetes,” Professor Wittert said.
The study results were presented at the ENDO 2026 conference in Chicago.
Type 2 diabetes remains one of Australia’s most common chronic health conditions, affecting more than 1.2 million people. The disease is strongly linked to abdominal obesity, poor diet and lack of physical activity, with men more likely than women to develop the condition.
Professor Wittert said newer medications such as Ozempic can play an important role in diabetes management, but they should be used alongside healthy lifestyle habits.
“Even with newer treatments for type 2 diabetes, a healthy diet and both resistance and aerobic exercise remain essential for the best overall health outcomes,” he said.
He also encouraged people to pay closer attention to waist circumference and overall metabolic health.
“Improving lifestyle habits can increase testosterone levels naturally, reduce body fat, build muscle and improve sexual function,” Professor Wittert said.
The study’s message is clear: while testosterone therapy may offer some health benefits for older men, maintaining a healthy weight, eating well and staying physically active remain the most effective ways to reduce the risk of type 2 diabetes.