A world-first study has revealed that resistance (weight) training not only preserves lean and muscle mass but also increases strength in people taking weight-loss medication.
Published today in Nature Medicine, the Tirzepatide and Resistance Exercise (T-REx) study is the first to show the effects of combining a GLP-1 medicine and resistance training on body composition, muscle mass, strength and a range of cardiovascular health measures.
Drugs such as semaglutide (Ozempic and Wegovy) and tirzepatide (Mounjaro) are commonly used for weight loss and have been found to improve chronic health conditions, reduce risk of obesity-related cardiovascular diseases, and enhance quality of life.
Lead investigator, Winthrop Professor Danny Green, from The University of Western Australia’s School of Human Sciences and HealthSpan Institute, said resistance exercise should be part of the prescription when people were using a weight loss drug such as tirzepatide.
The dramatic drop in body weight and fat mass delivered by GLP-1 medicines had raised questions about potential loss of lean and muscle mass, Professor Green said. (Lean mass is your body weight minus your body fat mass and includes muscles, organs, bones, skin and body water while muscle mass refers to the weight of muscle tissue in your body, which is mostly skeletal muscle).
“Loss of lean mass, including muscle, is an inevitable part of weight loss by any method – whether through diet and exercise alone, or medical or surgical interventions,” he said.
“With GLP-1 medicines now widely used and reducing body weight by an average of 20-25 per cent, and more than that in many people, it’s crucial that we understand how best to achieve optimal body composition and health in the weight-reduced state.
“We now know that muscle loss can be reduced and strength increased when regular resistance training is used alongside tirzepatide treatment.”
The 40-week study followed 120 men and post-menopausal women aged 50-to-70 years who were obese, or overweight with a weight-related health issue, but without type 2 diabetes, and prescribed tirzepatide for weight management.
Half the trial participants took part in three sessions of resistance training (weight training) each week and all received general advice on hydration, protein and fibre intake.
The participants taking tirzepatide experienced dramatic and rapid weight loss, regardless of whether or not they engaged in resistance training, with an average weight loss of 22.28kg in the trained group and 22.61kg in the untrained group after 40 weeks.
They also experienced an average loss of more than 17kg of fat mass (17.98kg in the trained group and 17.19kg in the untrained group).
Participants who did resistance training lost 25 per cent less lean tissue (including muscle) than those who did not. More importantly, the upper and lower body strength of the resistance training participants improved by 10 per cent, whereas it declined by 10 per cent in those who did not undertake resistance training.
Professor Green said the goal for those taking weight-loss drugs should be to improve their health and function, not just a lower number on the scales.
“This study shows that combining weight loss therapy and resistance exercise improves overall health,” Professor Green said.
“In theory, that should translate to a longer healthspan, the number of healthy, independent, and productive years of life that are lived free from debilitating chronic diseases.”
T-REx was an investigator-initiated study. The manufacturer of tirzepatide was not involved in the design, implementation or evaluation of the study, but did provide free medication for use in the trial.
UWA’s HealthSpan Institute is a flagship initiative led by Professor Green to extend human healthspan – the number of healthy, independent, and productive years of life free from debilitating chronic diseases.
The HealthSpan Institute will hold a free public lecture from 6-9pm on Thursday 26 November at the UWA Business School’s Wesfarmers Lecture Theatre. Join leading researchers, clinicians and health experts to hear the latest evidence on obesity treatment, including GLP-1 and other incretin-based therapies, and insights from the landmark TREx study.
The discussion will consider what we are learning about weight management, nutrition, sleep health, treatment side effects and patient experiences, as well as the broader opportunities and challenges of treating obesity.
Speakers will also explore what these developments could mean for preventing chronic disease, improving quality of life and supporting healthier ageing. Tickets are free but you need to register here.
