Objective Low 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.
Methods Using 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.
Results During 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.
Conclusion Adherence to both WHO guidelines for
waist circumference and physical activity is essential for
cancer prevention; meeting just one of these guidelines
is insufficient.