In the age of GLP-1 drugs, the old hierarchy of weight loss has been overturned. If “the leading actor” is defined as the intervention that moves the scale most dramatically, resistance training probably cannot win that role anymore. In major obesity trials, semaglutide 7.2 mg produced a mean body-weight reduction of 18.7% at 72 weeks, outperforming semaglutide 2.4 mg, while FDA-reviewed data for tirzepatide showed about 18% average loss at the highest approved dose after 72 weeks. By contrast, a large meta-analysis found that resistance training alone reduced body weight by only about 1.0 kg on average, even though it improved body composition and increased lean mass. (pubmed.ncbi.nlm.nih.gov)
But scale weight is not the only plotline. The more interesting question is what kind of body remains after the fat is gone. A recent JAMA Network Open analysis reported that GLP-1 receptor agonists were associated with mean fat-mass loss of 3.0 kg and lean-body-mass loss of 0.9 kg over a median of 24 weeks, with lean mass accounting for roughly 25% of total weight loss. In the SURMOUNT-1 body-composition substudy, tirzepatide reduced body weight by 21.3%, fat mass by 33.9%, and lean mass by 10.9% at week 72. So the muscle-loss concern is neither hysteria nor a reason to reject these drugs; it is a reminder that successful weight loss should be judged by function as well as by kilograms. (jamanetwork.com)
This is where strength training becomes indispensable. In a 2025 secondary analysis of a randomized trial, GLP-1RA treatment alone did not improve physical fitness beyond the gains already achieved with diet-induced weight loss, whereas exercise, with or without liraglutide, did; the combined program improved cardiorespiratory fitness by 10.3%, and absolute muscle strength was preserved. A follow-up analysis from the same trial found that after treatment stopped, weight regain was 6.0 kg greater after liraglutide than after exercise and 2.5 kg greater than after the combined approach. WHO’s 2025 guideline therefore frames GLP-1 therapy as part of a comprehensive strategy that may include structured diet and physical activity. So no, lifting weights is unlikely to retake the starring role in pure weight reduction. But in the GLP-1 era, it may become the editor of the script: the force that determines whether a person ends up merely lighter, or lighter and stronger. (link.springer.com)










