WHO guidelines on waist circumference and physical activity and their joint association with cancer risk.

objectiveLow body fat and high physical activity levels are key lifestyle factors in cancer prevention, but the interplay of abdominal obesity and physical activity on cancer risk remains unknown. We explored individual and joint associations of waist circumference and physical activity with cancer risk.

methodsUsing UK Biobank data (n=315 457), we categorised individuals according to WHO guideline thresholds for waist circumference and self-reported physical activity levels. Multivariable-adjusted Cox regression was used to estimate HRs and 95% CIs of total cancer. The reference group comprised individuals with recommended levels of waist circumference (<88 cm for women and <102 cm for men) and physical activity (>10 metabolic equivalent of task hours/week). Furthermore, we estimated the proportion of cancers attributable to abdominal obesity and insufficient physical activity.

resultsDuring a median follow-up period of 11 years (3 321 486 person-years), 29 710 participants developed any type of cancer. Participants not meeting the WHO guideline on waist circumference had increased cancer risk, even when sufficiently physically active according to the WHO (HR 1.11, 95% CI 1.08 to 1.15). Similarly, individuals not achieving the WHO guideline for physical activity showed an elevated risk, even if they were abdominally lean (HR 1.04, 95% CI 1.01 to 1.07). Not adhering to either guideline yielded the strongest increase in risk (HR 1.15, 95% CI 1.11 to 1.19). We estimated that abdominal obesity coupled with insufficient physical activity could account for 2.0% of UK Biobank cancer cases.

conclusionAdherence to both WHO guidelines for waist circumference and physical activity is essential for cancer prevention; meeting just one of these guidelines is insufficient.