Many people taking glucagon-like peptide 1 (GLP-1) drugs like Ozempic or Wegovy (semaglutide) and Mounjaro (tirzepatide) experience rapid weight loss. While weight loss can bring about health benefits, losing weight rapidly can also cause a decrease in muscle mass, lessen bone density, and lower your resting metabolic rate, leading to sarcopenia — the gradual loss of muscle mass, strength, and function.