Glucagon-like peptide-1 (GLP-1) receptor agonists and dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonists have transformed obesity management by producing substantial, sustained weight loss and improving metabolic health. Alongside these benefits, their effects on appetite, food intake, and gastrointestinal function have raised increasing interest in the nutritional consequences of pharmacologically induced weight loss. Although reductions in energy intake contribute to therapeutic efficacy, they may also influence protein intake, dietary quality, micronutrient adequacy, and skeletal muscle health, particularly in individuals with pre-existing nutritional vulnerability. This narrative review summarizes current evidence regarding nutritional considerations during GLP-1-based therapy, including changes in dietary intake, protein and micronutrient adequacy, body composition, muscle health, and nutritional assessment. Particular attention is given to populations at increased nutritional risk, practical approaches to nutritional monitoring, and strategies to support adequate nutrition during treatment. Current evidence suggests that nutritional responses to GLP-1-based therapy are heterogeneous and cannot be adequately evaluated using body weight alone. Assessment of dietary intake, body composition, muscle function, physical performance, and individual clinical characteristics provides a more comprehensive understanding of nutritional status than anthropometric measures alone. While routine supplementation or intensive monitoring is not supported for all patients, a risk-based and individualized approach appears appropriate, particularly for older adults and individuals with sarcopenic obesity, previous bariatric surgery, chronic gastrointestinal disease, or persistent treatment-related gastrointestinal symptoms. Future research should establish clinically meaningful nutritional outcomes and determine which nutritional interventions improve patient-centered outcomes during long-term obesity management.
