Avoiding obesity as well as maintaining a stable weight in middle adulthood could help prevent certain cancers in women, according to new research presented at this year’s European Conference on Obesity (ECO) in Vienna, Austria (23-26 May). Among the findings were that women with a high weight gain (an increase of 10kg or more across 6 years) were near twice as likely to develop pancreatic cancer. The study was conducted by Marisa da Silva and colleagues at the Arctic University of Norway, Tromsø, Norway.

Obesity and weight gain are well known to independently increase the risk of several cancers, often referred to as “obesity-related” cancers. Previous studies have shown that it’s not just having a high body mass index (BMI) that contributes towards an elevated cancer risk, but that a large gain in weight, irrespective of starting BMI is a contributory factor to the risk of certain cancers. However, there are few published studies in nationally representative populations of women on specific, obesity-related cancers, such as pancreatic and kidney cancer, in relation to prior weight change.

This study aimed to assess the respective roles of BMI and weight change on total and site-specific risk of obesity-related cancer in a large cohort of Norwegian women. It used self-reported questionnaire data from the Norwegian Women and Cancer study, linking this to information on cancer diagnosis from the Cancer Registry of Norway. These questionnaires were completed over the period 1991-2011 and asked about the weight, height, reproductive history, use of medication, and lifestyle of participants. The team then analysed this to determine BMI, weight change over a 6-year period, and the subsequent risk of obesity-related cancers defined as cancer of the breast (postmenopausal), colon-rectum, endometrium, ovary, pancreas, kidney, gallbladder, gastric cardia, liver, oesophagus (adenocarcinoma), meningioma, thyroid, and multiple myeloma.

The BMI analysis sample group consisted of 137,205 women and within this group there were 9,963 obesity-related cancer cases during an average follow-up time of 18 years. Obesity was found to increase the risk of postmenopausal breast cancer by 20%, and kidney cancer by 95%. Endometrial cancer saw the biggest risk increase in women with obesity who were more than twice as likely to contract the disease as women with normal weight.

The weight change sample group contained 82,001 women who were diagnosed with 5,329 obesity-related cancers during an average follow-up time of 13.7 years. High weight gain (defined as an increase of 10kg or more in 6 years) was associated with a 36% increased risk of postmenopausal breast cancer, a 40% increased risk of endometrial cancer. The strongest association was with pancreatic cancer, which saw a 91% increased risk. This is despite the fact that no link was found between BMI and the likelihood of developing pancreatic cancer.

The authors conclude that: “maintaining stable weight in middle adulthood, irrespective of baseline BMI status, as well as avoiding excess body weight are both of importance for prevention of several obesity-related cancers in women”. They also note that their finding of “increased risk of pancreatic cancer by moderate and high weight gain is novel”.

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