Abdominal obesity and associated factors according to gender and age in adults: a systematic review of observational studies

Abstract

Objective: To analyze the prevalence of abdominal obesity and associated factors according to gender and age in the adult population. Methods: A systematic review was conducted according to the PRISMA guidelines. The protocol was registered in PROSPERO (CRD420251141226). A search was performed in Web of Science, Scopus, and MEDLINE/PubMed for observational studies published between January 2020 and July 2025, in English or Spanish. Studies in adults that assessed abdominal obesity using waist circumference, waist-to-hip ratio, or waist-to-height ratio were included. Methodological quality was assessed using an adaptation of the Newcastle–Ottawa scale for cross-sectional studies, and the certainty of the evidence was assessed using GRADE. Due to methodological heterogeneity, a narrative synthesis was performed. Results: Twenty studies (n = 597,168) were included. The prevalence of abdominal obesity ranged from 3% to 81% (descriptive mean between studies: 38.4%; SD: 18.7), with higher estimates generally observed in women. The most reported associated factors were female gender, older age, urban residence, physical inactivity or sedentary lifestyle, and unhealthy eating habits. Abdominal obesity was associated with hypertension, type 2 diabetes mellitus, dyslipidemia, and metabolic syndrome. Conclusion: Abdominal obesity represents a significant global burden with a consistent sociodemographic pattern. The findings support gender- and age-based health promotion strategies as well as the need for standardized measurement and reporting.