Weight loss is a cornerstone of obesity management, but reductions in body weight are frequently accompanied by losses of fat-free mass and, potentially, skeletal muscle. Preservation of muscle mass, strength, and physical function is therefore an important component of high-quality weight loss. This narrative review summarizes current evidence on strategies for minimizing adverse changes in muscle-related outcomes during weight reduction. Recent evidence on dietary interventions, protein intake, exercise, bariatric surgery, and pharmacological treatment, particularly glucagon-like peptide-1 receptor agonists, was reviewed. Studies evaluating changes in fat-free mass, lean mass, skeletal muscle mass, muscle strength, and physical performance during weight reduction were considered. Caloric restriction consistently resulted in substantial reductions in body weight and fat mass but was also associated with variable losses of fat-free and lean mass. Greater energy restriction did not necessarily translate into proportionally greater benefits for body composition and, in some studies, was accompanied by greater lean mass loss. Higher protein intake appeared to support the preservation of lean tissue during energy restriction, particularly when combined with resistance exercise. Among exercise-based interventions, resistance training was most consistently associated with the preservation of lean mass and improvements in muscle strength and physical function, while aerobic exercise provided complementary benefits for cardiorespiratory fitness and walking capacity. Combined exercise may offer broader functional benefits. Bariatric surgery and GLP-1 receptor agonist therapy produced substantial weight loss but were also associated with reductions in lean mass, highlighting the importance of postoperative nutritional management, exercise, and monitoring of body composition alongside functional outcomes. Importantly, reductions in lean mass did not necessarily correspond to clinically meaningful impairments in muscle strength or physical performance. Overall, the quality of weight loss should be considered alongside the magnitude of weight reduction. An individualized approach integrating adequate protein intake, appropriate energy restriction, and structured exercise, particularly resistance training, may help minimize adverse changes in muscle health during obesity treatment. Bariatric surgery and pharmacological therapies should similarly be accompanied by strategies aimed at maintaining muscle mass and function. Future research should prioritize standardized assessment of skeletal muscle mass, strength, and physical performance and should specifically include individuals with sarcopenic obesity.
