The doctors included James Pavelka, MD, and Andrew Li, MD, of Cedars-Sinai Medical Center in Los Angeles.
If their finding is correct, it could lengthen the list of possible links between obesity and cancer.
They studied the records of 216 women undergoing surgery and treatment for ovarian cancer at Cedars-Sinai Medical Center.
The patients were in their late-50s to mid-60s, on average. They included 146 women with advanced ovarian cancer (stage III or IV ovarian cancer).
Ovarian cancer is hard to spot in its earliest, most treatable stages. That's a big reason why ovarian cancer has the highest death rate of any cancer of a woman's reproductive system.
The doctors checked the women's BMI (body mass index), which relates height to weight.
Among women with advanced ovarian cancer, 89 had normal BMI, 99 were obese or overweight, and 13 were underweight.
Average survival was shorter for overweight or obese women with advanced ovarian cancer.
"Our study suggests that fat tissue excretes a hormone or protein that causes ovarian cancer cells to grow more aggressively," Li says, in a Cedars-Sinai news release.
More research is needed to confirm that, Li notes.
While the women got similar types of treatment, it's possible that overweight or obese women may have needed higher chemotherapy doses. But that's not certain, due to incomplete records.