Background
Obesity prevalence has risen sharply worldwide, contributing significantly to the global burden of non-communicable diseases, including cancer. The impact of excess body weight (EBW) on cancer incidence and mortality is not uniform.
Objectives
This study aimed to estimate the population attributable fraction (PAF) and the number of cancer cases and deaths attributable to EBW, stratified by sex and HDI category.
Methods
We defined EBW as a body mass index (BMI) ≥25 kg/m². Relative risks (RRs) for EBW-related cancers were extracted from high-quality meta-analyses and systematic reviews. Cancer incidence and mortality data were obtained from GLOBOCAN 2022, while EBW prevalence was sourced primarily from WHO STEPS surveys. PAFs were calculated using Levin’s formula. Cancer types included were those classified by the International Agency for Research on Cancer (IARC) as causally linked to EBW. Estimates were disaggregated by sex and HDI category.
Results
The global prevalence of obesity was estimated at 12.0% (9.7% in men, 13.6% in women). Women in very high HDI countries had markedly higher obesity prevalence, while men showed more pronounced differences across HDI categories. Overweight prevalence was 25.6% globally, with higher rates in men (26.2%) than women (25.0%), particularly in high-HDI countries. Globally, EBW accounted for 3.4% of cancer incidence and 4.1% of cancer mortality. Sex-specific differences were pronounced as women had higher attributable fractions (3.9% incidence, 4.8% mortality) compared to men (2.9% incidence, 3.6% mortality). Endometrial cancer showed the highest incidence PAF (22.8%), followed by liver (15.6%) and kidney (15.3%) cancers. Women consistently exhibited higher PAFs across most cancer types, reflecting both biological susceptibility and higher obesity prevalence in many regions. Regional disparities were equally striking. Very high HDI countries had the greatest burden, with PAFs of 4.6% for incidence and 5.5% for mortality, reflecting higher obesity prevalence. High HDI countries followed closely (3.8% incidence, 4.7% mortality). In contrast, medium- and low-HDI regions had lower attributable fractions (2.8 and 3.0% incidence; 3.3 and 3.5% mortality). However, the mortality PAF for EBW was estimated to range over 8% in some medium and low-income countries, including Liberia (8.1%), Ghana (9.0%), Iraq (9.0%), Solomon Islands (10.0%), Guatemala (10.7%), and Egypt (11.6%).
Conclusions/Implications
EBW is a significant contributor to cancer incidence and mortality worldwide, but its impact varies by sex and region. Very high HDI countries show the greatest attributable fractions; however, over the past two decades, the sharpest increases in obesity prevalence have been observed in medium- and low-HDI countries, indicating that the cancer burden attributable to EBW in these regions is likely to rise substantially in the coming years. Furthermore, pronounced sex-related disparities in EBW prevalence and in PAF for both cancer incidence and mortality were identified in these settings. These findings underscore the need for region-specific strategies that take into account sex differences in obesity prevalence and cancer risk. Integrating obesity prevention into cancer control policies is essential, particularly in regions where obesity prevalence is rising fastest. Addressing both sex-specific vulnerabilities and regional disparities will be critical to reducing the global cancer burden attributable to EBW.