Overweight and obese
women who get plenty of exercise may have a lower risk of endometrial cancer
than if they were sedentary, according to new research.
Strenuous and moderate physical activity were linked to
lowered risk for heavy women, but there was no association between activity
level and endometrial cancer risk for thinner women, Christina M.
Dieli-Conwright of the Beckman Research Institute of City of Hope in Duarte,
California, and her colleagues found.
"Physical activity is a good thing, however its
involvement in reducing the risk specifically with endometrial cancer does need
to be further investigated," Dieli-Conwright told Reuters Health. While
the evidence is strong that both vigorous and moderate physical activity can
reduce breast cancer risk, she added, "with endometrial cancer it's not so
Some past studies have already linked increased
physical activity to reduced endometrial cancer risk, she and her colleagues
note in their report, published in the British Journal of Cancer.
To investigate whether a woman's body size might influence
that relationship, the researchers looked at 93 888 participants in the
California Teachers Study, 976 of whom were diagnosed with endometrial cancer
between study enrolment in 1995-1996 and the end of 2007.
Heavier women who reported at least three hours a week of
strenuous recreational physical activity at the beginning of the study had a
24% lower risk of developing endometrial cancer over the next dozen years
compared to women who got less than half an hour of vigorous exercise each
week, the researchers found.
But the same relationship was not seen for normal-weight
women. "Physical activity seems to be more strongly associated with lower
risk of endometrial cancer in overweight or obese women," Dr Alpa Patel,
an epidemiologist with the American Cancer Society in Atlanta, told Reuters
"We know that
one of the strongest risk factors for endometrial cancer is obesity, so when we
think of the ability to mitigate any of the excess risk through physical
activity, I think that's a very positive message," said Patel, who studies
exercise and cancer prevention but did not take part in the new study.
There are two mechanisms through which exercise might reduce
endometrial cancer risk, Patel added – by helping women lose weight and by
directly reducing circulating oestrogen levels. "Even in the absence of
weight loss, here we're seeing that there's a positive value of being
physically active to your risk of endometrial cancer," she said.
Although the connection was not seen among normal-weight women,
Patel said, other studies including her own research have suggested that exercise benefits them too.
The new study "definitely provides a bit more in terms
of that collective evidence base to be able to understand that relation between
physical activity and endometrial cancer risk," she said.