WA study reveals lifting weights is crucial to preserving muscle when taking weight-loss drugs like Mounjaro

People taking weight-loss drugs such as Mounjaro should be hitting the weights as well as shedding the kilos, with a landmark WA study finding resistance training can help preserve muscle and boost strength.

University of Western Australia researchers found that those taking the drug who lifted weights three times a week lost a similar amount of overall weight to those who did not train — but lost 25 per cent less lean tissue, including muscle.

The group who trained also increased their strength by 10 per cent, while strength in those who did not exercise fell by 10 per cent.

The study, published in medical journal Nature Medicine, followed 120 obese men and post-menopausal women aged 50 to 70, or people who were overweight and had a weight-related health condition other than type 2 diabetes.

All participants were prescribed tirzepatide (Mounjaro), with half undertaking three resistance-training sessions a week.

Both groups also received general advice on hydration, protein and fibre intake.

Over 40 weeks, the training group lost an average 22.28kg, including 17.98kg of fat mass.

Those who did not train lost an average 22.61kg, including 17.19kg of fat mass.

But the difference in muscle preservation was significant, with those who lifted weights losing 25 per cent less lean tissue than their counterparts.

Lead investigator Professor Danny Green, from UWA’s School of Human Sciences and HealthSpan Institute Winthrop, said the findings shed light on how to protect other aspects of health while taking appetite-suppressing medication.

“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.”

Professor Green said the findings confirmed the benefits of combining weight-loss medication with strength training.

“This study shows that combining weight loss therapy and resistance exercise improves overall health,” he 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.”