ADRB2 encodes the β2-adrenergic receptor, which is involved in regulating cardiovascular and respiratory function and lipolysis. This narrative review (PubMed/MEDLINE, Scopus and Web of Science Core Collection, to 8 October 2026; Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020-adapted flow diagram) summarises 48 primary association studies of ADRB2 polymorphisms, mainly Arg16Gly (rs1042713) and Gln27Glu (rs1042714), with athletic status, obesity, longevity, cardiovascular disease, asthma and chronic obstructive pulmonary disease (COPD); assesses their methodological quality; and critically examines meta-analyses. In athletes, mostly nominal associations link Gly16 and Glu27 with speed–strength status and Arg16Gly with endurance status, but a meta-analysis did not confirm an ADRB2 association with runner and cyclist status. Obesity and diet-response associations are inconsistent, varying by population and sex. The rs1042718–rs1042719 haplotype was associated with longevity only in Han Chinese men, and Glu27Glu with increased myocardial infarction risk only in a subgroup with a specific angiotensin I-converting enzyme (ACE) genotype. In meta-analyses, Glu27 is not associated with COPD risk in Asian or Caucasian populations. About half of the studies had fewer than 500 participants, almost none have been replicated, and many lack correction for multiple comparisons. The ADRB2 gene cannot serve as a tool for predicting athletic performance or for selection; its contribution should be studied as part of multimarker panels.