Resistance training cut lean mass loss on tirzepatide in a 120-person trial
In a 40-week randomized trial, adults on tirzepatide who added resistance exercise lost less lean tissue and gained strength, with the same weight loss.
Researchers at the University of Western Australia published in Nature Medicine a randomized controlled trial of resistance exercise added to tirzepatide. The study enrolled 120 adults with overweight or obesity, men and postmenopausal women aged 50 to 70 without type 2 diabetes. All received tirzepatide for 40 weeks; half were also assigned to resistance training three times a week, and the rest kept their usual activities nature.com
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Incretin mimetics used for obesity produce substantial weight and fat loss but also reduce lean soft tissue mass, which may impair skeletal muscle function, the authors note. The trial tested whether exercise can offset this loss. Most participants tolerated dose escalation to 15 mg weekly, and adherence to the exercise program was 91%.
Weight, fat and lean mass
Weight loss was similar in the two groups: 22.61 kg with tirzepatide alone and 22.28 kg with tirzepatide plus exercise (P = 0.694). Loss of total fat mass was also similar, 17.19 kg and 17.98 kg respectively (P = 0.700).
The difference appeared in lean soft tissue. Total lean soft tissue mass fell by 4.67 kg in the tirzepatide group and by 3.57 kg in the exercise group (P < 0.001). The between-group difference was 1.09 kg (95% CI 0.43–1.75 kg). Appendicular lean soft tissue mass fell by 3.55 kg versus 2.92 kg (P < 0.001) nature.com
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Muscle strength and limits
Strength decreased with tirzepatide alone: bench press by 4.09 kg, lat pulldown by 4.42 kg and knee extension by 4.42 kg. In the exercise group the same measures increased by 4.68 kg, 8.58 kg and 5.88 kg, respectively. All differences versus tirzepatide alone had P < 0.001.
The authors conclude that resistance training attenuated the loss of total lean soft tissue mass and is an effective adjunct to tirzepatide therapy. Tirzepatide itself was safe in the trial.
The study was relatively small and lasted 40 weeks, so it cannot show whether the strength gains persist for years or reduce future disability. It covered one age group and one medication, and results may differ in other populations.
