According to a new Swedish study obese women could reduce their cancer risk by reducing weight although the same does not hold in the case of men.

The study, by a team from Sahlgrenska University Hospital, Gothenburg, published in Lancet Oncology, has shown as much as a 42 % reduction in cancer levels with weight-loss surgery applying to a wide range of cancers though it is unclear it was the surgery that reduced the cancer risk.

In the study 2,010 obese patients who had bariatric (weight loss) surgery were compared with 2,037 obese patients who had received standard or no treatment. Patients received regular cancer screenings in the 11 years follow up period.

The researchers noted that patients who had undergone surgery lost an average of 19.9kg in weight, compared to an average of 1.3kg in the group who did not have surgery. They also reported that among the women the number of first-time cancers was significantly lower at (79) in the surgery group than in the non-surgery group at
(130).

For men however surgery appeared to have no effect on their cancer risk, with 38 cases recorded in the surgery group, and 39 in the non-surgery group.

Obesity has been known to be a culprit in many ailments and known to increase the risk of many types of cancer and is linked to 20% of all cancer deaths in women, and
14% in men in the western world.

Dr Andrew Renehan, a cancer expert at the UK's University of Manchester, said it was possible that weight-loss surgery had an impact on hormone levels in the body particularly as several common cancers are known to be linked to the female sex hormone estrogen in particular.

Dr Ian Campbell, medical director of the charity Weight Concern said, "In men, obesity is often goes hand in hand with a nutrient-poor diet, and lack of exercise and so even when weight loss has been achieved through surgery, unless these lifestyle issues are addressed, significant increased risk of some cancers will remain."

He added that "In obese men, the types of cancer most common are not so hormone sensitive and therefore not so directly influenced by weight loss."

Dr Julie Sharp, of the charity Cancer Research UK, said, "In the UK around 13,000 people a year could avoid cancer by maintaining a healthy bodyweight."