Waist circumference, physical activity, and cancer risk
Public health recommendations often emphasize two key factors in cancer prevention: maintaining a healthy body weight and engaging in regular physical activity. However, these two factors are often studied separately, even though they interact profoundly. Can the effects of abdominal obesity be offset by sustained physical activity? Or, conversely, can you be protected from the risk of cancer if you are sedentary but have a normal waist circumference?
This is far from a trivial question. Obesity, particularly the accumulation of visceral fat, is now recognized as a risk factor for several cancers: post-menopausal breast, endometrial, colon, pancreatic, liver, etc. Abdominal fat acts as an endocrine organ, secreting cytokines, hormones, and pro-inflammatory molecules that promote cell proliferation and disrupt hormone regulation. At the same time, a sedentary lifestyle and lack of physical activity also influence these same metabolic pathways, aggravating insulin resistance, increasing systemic inflammation, and reducing the effectiveness of the immune system.
But while these two factors (abdominal obesity and inactivity) share biological mechanisms, their exact relationship remains poorly understood. Body mass index (BMI), often used to estimate body size, does not distinguish between visceral fat and muscle mass. Waist circumference, on the other hand, better reflects abdominal fat, which is more directly linked to metabolic and cancer risk. On this basis, an international team of researchers sought to answer a simple but crucial question: which combination offers the most protection against cancer—a slim waist, good physical condition, or both?
The study
To answer this question, the researchers used data from the UK Biobank, a prospective cohort of more than 500,000 British participants aged 40 to 69 at the time of their inclusion between 2006 and 2010. This uniquely rich database compiles detailed information on health, lifestyle, diet, and biological parameters, as well as medical follow-up over more than a decade.
From this cohort, the researchers selected 315,457 participants after excluding individuals with cancer at baseline, extreme or missing values, and cases of underweight. The median follow-up period was 11 years.
Two main indicators were used: waist circumference and level of physical activity. Waist circumference was measured by trained personnel at the navel or the narrowest part of the trunk at exhalation. World Health Organization (WHO) thresholds were applied: >88 cm for women and >102 cm for men to define abdominal obesity.
Physical activity was estimated using the International IPAQ questionnaire, which assesses the duration and weekly frequency of moderate and vigorous activities over the past four weeks. The researchers calculated total energy expenditure expressed in MET-hours per week. According to WHO recommendations, a “sufficient” level of activity would correspond to more than 10 MET-hours/week, or approximately 150 minutes of moderate activity or 75 minutes of vigorous activity per week.
On this basis, participants were divided into four groups:
- Slim waist + sufficient physical activity (reference group)
- Slim waist + insufficient activity
- Abdominal obesity + sufficient activity
- Abdominal obesity + insufficient activity
The researchers then monitored the occurrence of any type of primary cancer, as confirmed by national registries. The analyses were adjusted for numerous factors: age, sex, education level, socioeconomic status, smoking, alcohol consumption, diet, physical inactivity, family history of cancer, screening, and preexisting chronic diseases (diabetes, cardiovascular disease).
Sensitivity analyses were conducted to verify the robustness of the results: exclusion of cancers that appeared in the first two or five years (to avoid reverse causality bias), separate analyses by gender and non-smokers, and the use of activity data measured by accelerometer in a subgroup of 72,000 participants.
Results & Analysis
A total of 29,710 cases of cancer were diagnosed during the follow-up period. The main results showed that neither a slim waist alone nor physical activity alone is sufficient to fully reduce the risk of cancer. The two parameters play a complementary and inseparable role. This study is the first to demonstrate, in a large population, that abdominal obesity and physical inactivity have independent and additive effects on cancer risk. In other words, it is not enough to compensate for one with the other: a physically active but abdominally obese individual remains at increased risk, as does a thin but sedentary individual.
People with abdominal obesity had an 11% higher overall risk of cancer than those with a normal waist size, even when they were active according to WHO recommendations. The hazard ratio (HR) for this group was 1.11 (95% CI: 1.08–1.15). In those who were both abdominally obese and physically inactive, the risk rose to 1.15 (95% CI: 1.11–1.19). Conversely, individuals with a slim waist but who were insufficiently active also had an increased risk, albeit more moderate, with an HR of 1.04 (95% CI: 1.01–1.07) . In other words, being slim but sedentary does not eliminate the risk. The most favorable scenario was for physically active individuals with a normal waist circumference, who served as the reference group.
The analyses remained consistent across all scenarios tested:
- Even after excluding the first five years of follow-up, the risk remained significantly higher for people who were abdominally obese and inactive (HR 1.20).
- Among non-smokers, the relative risk was 1.18, confirming the independence of the link from tobacco use.
- The results were similar when activity was measured using an accelerometer, with an HR of 1.22, reinforcing the credibility of the self-reported data.
When focusing on cancers specifically linked to obesity or physical inactivity (postmenopausal breast, endometrial, liver, colon, and pancreatic), the differences were even more pronounced: the risk increased by 38% for obese but active individuals and by 48% for obese and inactive individuals, compared to the reference group.
The researchers estimated that 2% of all cancers in the cohort could be attributed to the combination of these two modifiable factors: abdominal obesity and inactivity. This may seem small, but when applied to the UK population, it would represent more than 12,000 preventable new cases of cancer each year.
Biologically, these findings are consistent with current knowledge. Visceral fat secretes pro-inflammatory cytokines (IL-6, TNF-α), promotes hyperinsulinemia, and increases circulating levels of IGF-1, all of which are involved in cell proliferation and tumor cell survival. At the same time, physical inactivity reduces energy expenditure, insulin sensitivity, hormone regulation, and immune defenses. These two pathways, although partially distinct, reinforce each other.
Researchers point out that good physical condition does not completely protect against the risks associated with abdominal fat, as it has systemic endocrine effects that outweigh the metabolic benefits of exercise. Similarly, having a slim waist but remaining inactive deprives the body of essential regulation: stimulation of immunity, reduction of inflammation, and improvement of mitochondrial and hormonal function.
These data also highlight the limitations of BMI as a risk indicator. A person who is “thin” in terms of total weight may have a significant accumulation of visceral fat and therefore a high risk, while a more muscular individual with a slightly higher BMI may be better protected. Waist circumference appears here to be a much more relevant marker, directly linked to the pathophysiological mechanisms of cancer.
Finally, beyond the biological aspects, this study highlights a public health issue: prevention depends as much on the environment as on individual behavior. Promoting physical activity requires urban planning, education, and health policies that are accessible to all. However, the populations most exposed to sedentary lifestyles and obesity are often those with fewer opportunities to exercise or eat healthily. This needs to become a collective priority, not just an individual responsibility.
Practical applications
This study of more than 300,000 individuals indicates that cancer prevention could involve both exercise and controlling abdominal fat. Being active does not compensate for the harmful effects of excess waist circumference, just as being thin does not compensate for inactivity. Health depends on the synergy between the two. Promoting this dual approach (being more active and reducing waist size) is one of the most powerful and simplest public health strategies to implement.
In concrete terms, aiming for 150 minutes of moderate activity (brisk walking, cycling, swimming, light running, or group activities) per week remains the minimum. But it’s not just about moving; you also need to reduce visceral fat. This requires a balanced diet, a reduction or even total elimination of ultra-processed foods and excess calories, and regular activity combining endurance and muscle strengthening.
Measuring waist circumference should once again become a reflex during consultations, just like blood pressure. Simple, inexpensive, and reproducible, it provides direct information on metabolic risk. A value greater than 88 cm in women and 102 cm in men should be cause for concern, even if the overall weight (or BMI) appears normal. Women should aim for a value less than or equal to 80 cm, and men less than or equal to 94 cm.
Finally, this study reminds us that cancer prevention is not based solely on screening or treatment, but on an overall lifestyle. Maintaining a healthy waist size and staying active are two complementary pillars: one acts on the metabolism, the other on physiology and the immune system. In a world where abdominal obesity affects nearly half of all adults and a third of the population remains sedentary, the combination of sufficient physical activity and a healthy waist circumference is not just beneficial: it is essential.
Reference
Bohmann, P., Stein, M. J., Amadou, A., Baurecht, H., Fervers, B., Fontvieille, E., Freisling, H., Friedenreich, C., Konzok, J., Peruchet-Noray, L., Leitzmann, M. F., Sedlmeier, A. M., & Weber, A. (2025). WHO guidelines on waist circumference and physical activity and their joint association with cancer risk. Br J Sports Med.
