Weighing the risk: a scoping review on the relationship between obesity and glioma

Obesity is well-documented to increase the risk and worsen the prognosis of various cancers. This review investigates the relationship between obesity and glioma, as a comprehensive analysis has not been conducted. A literature search was conducted across several databases, including ScienceDirect, PubMed, and Google Scholar, from 2004 to 2025, using the keywords: (glioblastoma OR glioma OR GBM) AND (obesity OR "body mass index" OR BMI OR overweight OR adiposity OR "waist circumference") AND (risk OR association OR prevalence OR incidence OR correlation OR etiology). Inclusion criteria focused on studies in English published from 2004 to 2025. From an initial screening of 606 studies, 26 met the criteria.The role of high BMI or waist circumference (WC) as a risk factor remains unclear, with evidence varying by age, gender, and tumor grade. The compound effect of high BMI with high WC is more pronounced in women. Evidence of linearity between BMI and glioma risk is also stronger in women. Notably, low BMI combined with high waist circumference presents a greater risk than high BMI with high waist circumference. Healthy lifestyle factors may influence glioma risk more significantly than BMI. Additionally, elevated BMI in early life (18-21yo) is more consistently associated with increased glioma risk, while height is identified as a common risk factor. Although several studies associate higher BMI with poorer overall survival (OS) and progression-free survival (PFS), some suggest that being overweight may confer a survival advantage compared to normal or underweight individuals. Obesity impacts prognosis more significantly in MGMT-methylated gliomas. Further research is needed to clarify these complex associations.