A major new study from Sweden has found that waist circumference (WC)—a simple measure of abdominal fat—may be a more accurate predictor of obesity-related cancer risk in men than the more commonly used body mass index (BMI).
The findings were presented at the European Congress on Obesity (ECO 2025) and published in the Journal of the National Cancer Institute.
While BMI has long been used to assess body weight and cancer risk, it only reflects general body size and doesn’t distinguish between muscle and fat or reveal where fat is stored.
Waist circumference, on the other hand, gives insight into abdominal fat, particularly visceral fat, which surrounds internal organs and is known to have harmful effects on health.
The study, led by researchers Dr. Ming Sun, Dr. Josef Fritz, and Dr. Tanja Stocks from Lund University in Malmö, Sweden, analyzed health data from 339,190 adults who had undergone BMI and waist measurements between 1981 and 2019.
Most of the participants (61%) had their measurements taken by health professionals, while the rest were self-reported. The average age was 51 years.
Researchers tracked these individuals over a median of 14 years using the Swedish Cancer Register. During this time, 18,185 cases of obesity-related cancers were recorded, including cancers of the colon, liver, pancreas, postmenopausal breast, ovary, and more—types strongly linked to excess body fat.
To fairly compare WC and BMI (which are measured on different scales), the researchers used a standard approach that allowed them to assess the risk of cancer per a similar amount of increase in each measurement.
In men, the results showed that:
- An 11 cm increase in waist size (e.g., from 90 cm to 100.8 cm) was linked to a 25% higher risk of developing obesity-related cancers.
- A 3.7 kg/m² increase in BMI (e.g., from 24 to 27.7 kg/m²) was linked to a 19% higher risk.
- Even after accounting for BMI, a larger waist remained an independent risk factor for cancer, suggesting that abdominal fat itself carries unique cancer risks beyond general body size.
In women, the results were different:
- A 12 cm increase in waist size and a 4.3 kg/m² increase in BMI were each linked to only a 13% higher risk.
- Unlike in men, WC did not provide much additional information beyond BMI, meaning that waist size alone wasn’t as strong a risk marker in women.
Why the Difference?
The researchers believe the sex-based differences have to do with how men and women store fat:
- Men are more likely to carry fat around their abdomen, where it becomes visceral fat, which is more active in driving health problems like inflammation and insulin resistance.
- Women, especially before menopause, tend to store more subcutaneous fat in the hips and thighs, which is less harmful metabolically.
This may explain why waist size is a better marker of harmful fat in men than in women.
Additionally, hormonal differences may play a role. Fat affects sex hormones differently in men and women, and these hormones can influence cancer development in distinct ways. Men may also produce more insulin in response to abdominal fat, which has been linked to higher cancer risk.
The researchers suggest that combining waist and hip measurements, especially for women, could help better estimate cancer risk, since this provides a fuller picture of fat distribution. Future studies using more detailed body fat measurements—like body scans—may offer even clearer insights.
This large, well-designed study provides compelling evidence that waist circumference is a more reliable indicator of obesity-related cancer risk in men than BMI.
It highlights the limitations of using BMI alone to assess cancer risk and supports the idea that where fat is stored matters as much as how much fat a person has.
For women, the findings are more nuanced. While higher waist size is still linked to increased cancer risk, it doesn’t seem to add much predictive value beyond BMI. This may be due to the fact that BMI already captures most of the relevant fat distribution in women, or that fat affects their cancer risk through different biological pathways.
Importantly, the study emphasizes the need for sex-specific approaches when assessing cancer risk and designing prevention strategies. It also calls for more precise tools to measure body fat, rather than relying solely on BMI or even waist size.
In conclusion, measuring waist size—especially in men—may help doctors better identify individuals at higher risk for certain cancers. It’s a simple, low-cost tool that could improve cancer prevention efforts when used alongside other health assessments.
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The research findings can be found in Journal of the National Cancer Institute.
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