Researchers found obesity was consistently connected to lower rates of breast and cervical cancer screening among white women in a review of 32 previously published studies. Fourteen studies focused on cervical cancer, 10 on breast cancer and eight looked at colorectal cancer.

Sarah S. Cohen and colleagues at the University of North Carolina, Chapel Hill, report the findings in the online edition of the journal Cancer.

The National Cancer Institute recommends that women have a mammogram to detect breast cancer every one to two years, starting at age 40, and a Pap test to screen for cervical cancer at least once every three years, beginning about three years after they start having sex.

It's not certain why obese women are less likely to get these screening tests, as few studies have been designed to look at the underlying reasons, according to Cohen and her colleagues. However, they point out, some research shows that obese women often worry about embarrassment in the exam room, negative reactions from health care providers and "lectures" about their weight.

One of the studies in the review also found that obese women often complained that the gowns, exam tables and equipment at doctors' offices were too small for them.

Another possibility, according to Cohen's team, is that doctors less often recommend cancer screening to obese women than to thinner women. But there was a lack of evidence supporting this in the studies reviewed. One study found that obese women were more likely to say their doctor had advised them to get a Pap test.

The findings suggest more should be done to encourage obese women, particularly obese white women, to get regular mammograms and Pap tests, according to Cohen and her colleagues.