Compared to women of normal weight, those with obesity are 24% more likely to develop one of a handful of cancers linked to the condition, and their chances of developing cancers of the kidney or endometrium were around twice as high as those of normal-weight women, new research has found.
In a Norwegian study that tracked 137,205 women between 30 and 70 years old, researchers also found that those who gained more than 22 pounds over a period of five to eight years were nearly twice as likely as those who maintained a stable weight to develop pancreatic cancer.
For women with such a substantial weight gain over just a few years, the risk of endometrial cancer and post-menopausal breast cancer increased by an average of 40% and 36%, respectively.
The new research capitalized on Norway's universal healthcare system and its meticulous record-keeping to analyze women, their weight and their cancer status over 18 years. The results will be presented Thursday at this year's European Conference on Obesity (ECO) in Vienna, Austria.
In a range of studies, researchers have linked obesity with higher rates of 13 different types of malignancies: cancers of the breast after menopause, the colon and rectum, the endometrium, ovary, pancreas, kidney, gallbladder, gastric cardia, liver, esophagus, meningioma, thyroid and the blood cancer multiple myeloma.
The new study found that ovarian and rectal cancers were not linked either to excess weight or rapid weight gain among the women tracked — something of a surprise. And while rates of colon, rectal and kidney cancers were higher among obese women than normal-weight women in the Norwegian study, those differences did not reach statistical significance. In short, they were small enough that they might have been due to chance.
The links between obesity and heart disease, and between obesity and diabetes, have long dominated discussion of the health effects of excess weight. But obesity and lack of physical activity are collectively considered the second-most-common risk factor for cancer, behind smoking.
Still, researchers are in the relatively early stages of teasing out the relationship between obesity and cancers, and the Norway study will help contribute to that.
Among the lines of research it will likely help stimulate are explorations of the mechanisms by which carrying — or in some cases, gaining — excess body fat contribute to the risk of certain cancers. In the cases of breast and endometrial cancer, for instance, scientists have focused on the penchant of stored fat to perturb sex hormones.
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