According to a Swedish study, obese women who have bariatric surgery to lose weight, could be lowering their risk of cancer by doing so.

Many types of cancer are directly linked to obesity and a high body mass index (BMI), with 14% of cancer deaths in men and 20% in women caused by obesity. This makes obesity the second most preventable cause of cancer, next to smoking.

The study compared 2,010-obese patients who under-went bariatric surgery with 2,037-obese patients on standard or no treatment, who were followed for about 11-years and who received regular cancer screenings.

Over the study period, patients who under-went surgery lost an average of 19.9-kg., compared to an average of 1.3-kg. for those who did not have surgery.

Among women, at 79 the number of first-time cancers was significantly lower in the surgery group, compared to 130 in the non-surgery group.

While, the surgery had no significant effect on cancer risk in men, with 38 cases recorded in the surgery group, and 39 in the non-surgery group, though researchers found women who under-went weight loss surgery reduced their risk for cancer by 42%. The beneficial effect of weight-loss surgery on women seemed to apply to a wide range of cancers.

Published in Lancet Oncology, experts believe surgery's impact on hormone levels may hold the key, suggesting the surgery has a more subtle impact on cancer risk, such as, weight-loss surgery reducing the amount of hormone-producing fat cells in the body.