Obesity represents a global public health challenge, with specific characteristics and needs in adolescent and elderly populations. GLP-1 (glucagon-like peptide-1) receptor agonists such as liraglutide and semaglutide, as well as the GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptor co-agonist tirzepatide, have emerged as promising therapeutic options for obesity management. This review analyzes the clinical development, efficacy, safety, and tolerability of these drugs specifically in adolescents and the elderly, populations typically underrepresented in initial clinical trials. Findings from pivotal clinical studies and real-world data are detailed, showing that these medications offer significant benefits in weight reduction, albeit with particular safety considerations for each age group. Additionally, emerging GLP-1 molecules in clinical development with potential application in these special populations are explored. The conclusions emphasize the need for a personalized approach considering the specific pathophysiological, pharmacokinetic, and pharmacodynamic differences of each population group.