Stomach Stapling May Lower Cancer Risk in Women

Researchers also tracked 2,037 obese people who did not have the surgery. For patients who got their stomachs stapled, most lost about 20 kilograms (44 pounds). In people who did not have the surgery, most gained a little over 1 kilogram (2 pounds, 3 ounces).

Of the women who had the surgery, 79 got cancer. In the non-surgery group, 130 women got cancer. Various types were seen, including breast, skin and blood cancer.

Among the men, 38 of the men who had the surgery got cancer versus 39 men in the non-surgery group.

The study was paid for by the Swedish Research Council and others, including drug makers Hoffman La Roche, Astrazeneca and Sanofi-Aventis, whose products include diet drugs.

Experts were baffled why only women appeared to have a lower cancer risk after the weight-loss surgery.

Lars Sjostrom of Sahlgrenska University Hospital in Sweden and the paper's lead author, said it was possible there weren't enough men in the study to see an effect -- men only made up about a quarter of the participants.

Sjostrom and colleagues also found that neither weight loss without surgery or reduced calorie intake appeared to affect cancer rates among either men or women. He added that other possibilities to explain the smaller cancer risk, including genetics, were now being considered. "There is an unknown factor behind this effect, but we have no idea what it is," he said.

Lichtenfeld hypothesized that the stomach surgeries might have different effects on hormones or some other substance in the body that ultimately reduced the chances of developing cancer.