Obese women '40% more likely to develop cancer in their lifetime'

Women who are obese are around 40% more likely to develop certain forms of cancer than those of a healthy weight. This is according to new estimates calculated by Cancer Research UK.

Obese women are at a 41% higher lifetime risk of developing a weight-related cancer than women of a healthy weight, the new statistics show.

Obesity - defined as having a body mass index (BMI) of 30 or higher - is a major problem in the USA, affecting more than a third of adults and almost a fifth of children and adolescents.

It is well established that obesity can increase cancer risk. 

According to the American Cancer Society, excess body weight may contribute to cancer development through a number of mechanisms. It can interfere with immune system function, for example, or affect levels of hormones - such as estrogen and insulin - to drive cancer development.

A statistical information team at Cancer Research UK set out to get a better idea of how obesity affects an individual's lifetime risk of developing one of seven cancers that have previously been associated with weight: breast (postmenopausal), bowel, pancreas, esophageal, uterus (endometrium), kidney and gallbladder.

To reach their estimates, the team assessed data on lifetime cancer risk in the UK population, data on overweight and obesity among UK women, as well as the results of a 2011 study published in the British Journal of Cancer that analyzed the link between overweight and obesity and cancer development.

274 obese women in every 1,000 will develop a weight-related cancer during lifetime

The team calculated that women who are obese are 41% more likely to develop one of the seven cancers, compared with women who are a healthy weight.

Fast facts about obesity

• Around 78.6 million adults in the US are obese
• Obesity is most common among Americans aged 40-59
• As well as increasing the risk of certain types of cancer, obesity can raise the risk of stroke, heart disease and diabetes.

In detail, the researchers estimated that in a group of 1,000 obese women, 274 are likely to be diagnosed with a weight-related cancer, compared with 194 in a group of 1,000 women of a healthy weight.

The following shows the increased lifetime cancer risk for obese women by cancer type, compared with women of a healthy weight:

• Breast cancer (postmenopausal) - 25%
• Pancreas cancer - 31%
• Bowel cancer - 32%
• Kidney cancer - 78%
• Gallbladder cancer - 100%
• Uterus (endometrium) cancer - 131%
• Esophageal cancer - 133%.

These figures add to a growing body of research highlighting the importance of weight in cancer development. In August 2014, another team of researchers reported on a study published in The Lancet, in which researchers from the London School of Hygiene & Tropical Medicine in the UK linked overweight and obesity to increased risk of 10 common cancers, including leukemia and cervical cancer.

"We know that our cancer risk depends on a combination of our genes, our environment and other aspects of our lives, many of which we can control - helping people understand how they can reduce their risk of developing cancer in the first place remains crucial in tackling the disease.

Lifestyle changes - like not smoking, keeping a healthy weight, eating a healthy diet and cutting back on alcohol - are the big opportunities for us all to personally reduce our cancer risk. Making these changes is not a guarantee against cancer, but it stacks the odds in our favor."

References:

1.  Cancer Research UK news release, accessed 17 March 2015.
2.  Additional source: CDC, Adult obesity facts, accessed 17 March 2015.