Waist circumference stronger risk marker than BMI for obesity-related cancer in men, but not women

Body size and excess weight, conventionally assessed using body mass index (BMI), are well-established risk factors for many types of cancer. However, new research to be presented at this year’s European Congress on Obesity (ECO 2025, Malaga, Spain, 11-14 May) and published in The Journal of the National Cancer Institute shows that waist circumference (WC) is a stronger risk marker than BMI for developing obesity-related cancers in men, but not women. The study was conducted by Dr Ming Sun, Dr Josef Fritz and Dr Tanja Stocks, Lund University, Malmö, Sweden, and colleagues.

The study analysed data from 339,190 individuals collected from various Swedish populations who had undergone health assessments with BMI and WC assessments from 1981-2019 (61% objectively measured, 39% self-reported, mean age 51.4 years). Cancer diagnoses were obtained from the Swedish Cancer Register.

Established obesity-related cancers were defined as those for which the International Agency for Research on Cancer (IARC) has concluded there is sufficient evidence linking them to obesity, including cancers of the oesophagus (adenocarcinoma), gastric (cardia), colon, rectum, liver/intrahepatic bile ducts, gallbladder, pancreas, breast (postmenopausal), endometrium, ovary, renal cell carcinoma, meningioma, thyroid, and multiple myeloma.

The authors calculated relative risks associated with obesity-related cancers for WC and BMI, taking into account multiple factors that could influence the results, such as age, smoking habits, and sociodemographic factors including education level, income, birth country and marital status.

Because WC is harder to measure accurately and consistently than BMI, its values tend to vary more. To ensure a fair comparison, the researchers adjusted for measurement errors in both WC and BMI. This adjustment makes the calculated relative risks of WC and BMI more directly comparable. Finally, because WC and BMI are measured on different scales (1 standard deviation [SD] = 3.7 and 4.3 kg/m² for BMI for males and females respectively, and 10.8 and 11.8 cm for WC for males and females respectively), calculating relative risks per 1-SD increase ensures that the increments for WC and BMI represent comparable magnitudes, allowing for a direct comparison of their associated relative risks.

During a median follow-up of 14 years, 18,185 established obesity-related cancers were recorded. In men, a WC increase of approximately 11 cm (e.g., comparing a WC of 100.8 cm versus 90 cm) was associated with a 25% higher risk of developing obesity-related cancers. By comparison, a BMI increase of 3.7 kg/m² (e.g., comparing BMI of 27.7 kg/m² versus 24 kg/m²) corresponded to a 19% increased risk. Additionally, after accounting for BMI, high WC still remained a risk factor for obesity-related cancer in men. This suggests that the elevated risk associated with abdominal adiposity is specific, and not explained by high body size alone, as measured by BMI.

Among women, the associations were weaker and similar for both WC and BMI. For example, both an increase of about 12 cm in waist circumference (e.g., comparing WC of 91.8 cm vs. 80.0 cm) and an increase of 4.3 kg/m² in BMI (e.g., BMI of 28.3 kg/m² vs. 24 kg/m²) were both associated with a 13% higher risk of developing obesity-related cancers.

The authors explain: “BMI is a measure of body size, but does not provide information on fat distribution, whereas waist circumference is a proxy more closely related to abdominal adiposity. This distinction is crucial because visceral fat, which accumulates around the abdominal organs, is more metabolically active and has been implicated in adverse health outcomes, including insulin resistance, inflammation, and abnormal blood fat levels. Consequently, individuals with similar BMIs may have distinct cancer risks due to differences in fat distribution.”

On the difference between men and women, they reflect: “A plausible explanation is that men are more likely to store fat viscerally, while women generally accumulate more subcutaneous and peripheral fat. Consequently, waist circumference is a more accurate measure of visceral fat in men than in women. This may make waist circumference a stronger risk factor of cancer in men, and explain why waist circumference adds risk information beyond that conveyed by b in men, but not women.”

They suggest: “Including hip circumference into risk models may provide further insights into this sex difference and enhance the association between WC and cancer, particularly for women – this is because, especially in women, the combination of waist circumference and hip circumference give a better estimation of visceral fat than waist circumference alone.”

They go on to explain that research has indicated that adiposity, especially central adiposity, leads to higher concentrations of circulating insulin in men than in women. This may also partly explain why WC is more strongly associated with cancer risk in men. They say: “The divergence in how waist circumference and BMI relate to cancer risk between men and women underscores the complexity of the impact of adiposity on cancer development. It suggests that considering biological and physiological differences between the sexes might be helpful when assessing cancer risk. Further research is needed to explore these sex differences.”

They conclude: “Our study provides evidence that waist circumference is a stronger risk factor than BMI for obesity-related cancers in men, but not in women. Additionally, waist circumference appears to provide additional risk information beyond that conveyed by BMI in men. The weaker contribution of WC beyond that of BMI in women may result from sex-specific interactions with adiposity measures, such as with sex hormones, on obesity-related cancer risk, or differences in how waist circumference and BMI reflect body fat in men vs. women. Future research incorporating more precise measures of adiposity, along with comprehensive data on potential confounding factors, could further elucidate the relationship between body fat distribution and cancer risk.”