Fat Chance: Obesity and Cancer Risk

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  Last updated March 6, 2017 at 3:25 pm

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Could those extra kilos carry an increased risk of cancer? According to a large review study from England, the extra weight can carry an extra risk of getting a wide range of some of the most deadly cancers.


As reported today in the medical journal BMJ, a review of over 200 studies conducted worldwide clearly shows strong evidence that obesity increases your chances of getting a variety of cancers, particularly those associated with the digestive tract and the hormone system. There could be further associations between obesity and other cancers, but these links remain uncertain because the quality of evidence is not particularly strong. But, with the prevalence of obesity more than doubling over the past 40 years and cancer as the leading cause of death worldwide, these strong links between the two are of serious concern.


The international team of researchers, led by two researchers from Imperial College London analysed 49 publications covering 204 studies that looked at obesity measurements (such as body mass index (BMI), weight gain, and waist circumference) and 36 different types of cancer.


Strong associations were found between elevated BMI and the risks of oesophageal, bone marrow, biliary tract system, pancreatic and kidney cancers. Men also showed an increased risk of colon and rectal cancers with elevated BMI while premenopausal women showed an increase risk for endometrial cancer. Obese postmenopausal women have a strong association with breast cancer (if they have not had hormone replacement therapy) and endometrial cancer (if they did have HRT).


There was also a weaker but highly suggestive association detected between BMI and waste circumference with colon cancer, liver cancer, postmenopausal breast cancer and endometrial cancers.


The scale of the various risk associations identified varies with a 5 kg increase in BMI giving a 9% increased risk for colorectal cancer among men through to a 56% increased risk for biliary tract system cancers. Risk of postmenopausal breast cancer among women who never used hormone replacement therapy increased by 11% for each 5 kg of weight gain while the risk of endometrial cancer increased by 21% for each 0.1 increase in waist to hip ratio.


The researchers point out that this analysis was a review of previous studies that can identify correlations but cannot make firm conclusions about cause and effect. So, while they cannot say why obesity causes cancer, they strongly urge weight loss for obese people as a positive strategy toward avoiding cancer.



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About the Author

Paul Willis
Paul is a respected leader in the science community with an impressive career in science. He has a background in vertebrate palaeontology, studying the fossils of crocodiles and other reptiles. He also has a long history as a science communicator, with a career spanning as Director of The Royal Institution of Australia, presenter and host for Australia’s Science Channel, working for the ABC on TV programs such as Catalyst and Quantum as well as radio and online. He’s written books and articles on dinosaurs, fossils and rocks and is finding new ways to engage the people of Australia with the science that underpins their world. Follow him on Twitter @fossilcrox.

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The Royal Institution of Australia is an independent charity, and the sister organisation of the prestigious Royal Institution of Great Britain, tasked with promoting public awareness and understanding of science.


The Royal Institution of Australia is passionate about building and connecting communities engaged with science, and as such works closely with scientific organisations, institutions, universities from Australia, and leaders to inspire the next generation of innovators and to create a lasting legacy for Australia.


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