Does bariatric surgery reduce cancer risk?

By | November 13, 2018

There is adequate evidence that excess body fat results in an increased risk of 13 different cancers, according to the International Agency for Research on Cancer (IARC).  

In a 2016 reassessment of the preventive effects of a healthy weight on cancer risk, the France-based IARC reviewed over 1000 epidemiologic studies, which examine disease distribution in populations.

The strength of the evidence was deemed ‘sufficient’ in 13 cancers, including cancer of the oesophagus, part of the stomach (gastric cardia), colon and rectum, liver and gallbladder. There was also sufficient evidence for pancreatic, thyroid, ovary and post-menopausal breast cancer.

In patients with breast cancer, but not other cancers, a significant amount of evidence pointed to an increased BMI around the time of cancer diagnosis, as well as reduced survival.  

“In 25 years obesity will [overtake] smoking as the main [preventable] cancer cause in women in the UK,” Bariatric (Obesity) Surgeon, Dr Douraid Abbas said, referring to a report by Cancer Research UK.

28 per cent of Australian adults were obese in 2014-15, an increase from 19 percent in 1995. 22,700 weight loss surgeries were reported in 2014-15, versus 9,300 in 2005-06, according to the Australian Institute of Health and Welfare.

“Almost [13 percent of people in regional Western Victoria,] and almost 12 percent of the Australian population have a BMI over 40; that’s the highest class of obesity, Class 3 or morbid obesity…We haven’t been this big ever and the rate is increasing alarmingly,” Abbas, based in Ballarat, said.

“Only five per cent of obese individuals reach a healthy weight with exercise and diet, and less than one per cent maintain that weight loss over a year. Obesity is a disease influenced by three components: lifestyle, environment and genetics. [Once you are obese], it’s very hard to lose the weight.

“The brain finds a diet high in sugar, salt and saturated fat, and a sedentary lifestyle with low energy expenditure confusing, which may cause the anti-famine genes to be activated – [a result of the] interaction between environment and genes.”

When is weight loss surgery an option?

Bariatric surgery is a keyhole procedure that reduces the size of the stomach and decreases appetite. It is currently used for individuals with a BMI over 35 with metabolic syndrome – a cluster of coexisting conditions including high blood sugar, high cholesterol and excess body fat around the waist. Metabolic syndrome increases heart disease, stroke and type 2 diabetes risk.  

The surgery is also an option for type 2 diabetics with a BMI over 30 (Class 1 obesity), whose condition is not well controlled on their medication, Abbas said.  

“Bariatric surgery is a very powerful tool to reset the brain and weight loss will ensue after that. But the patient needs to learn that it’s a tool and a commitment.”

A 2013 comprehensive review of the literature on the effect of bariatric surgery on cancer outcomes suggested that the surgery did reduce cancer risk, particularly for breast and endometrial cancer in individuals who had been obese prior.

However the studies were lacking in number and quality and so the findings were deemed inadequate for a formal evaluation.

Regardless, Abbas said it is important to acknowledge the sufficient evidence regarding the “13 obesity-cancers.”

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