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HealthHow weight loss reduces your cancer risk

It’s never too late for weight loss and doing so could save you from developing any one of 13 different cancers. That’s the message of a remarkable new piece of research carried out by the world-renowned Cleveland Clinic in the US. In a study involving over 30,000 patients, researchers found that obese adults who lost weight thanks to bariatric surgery — put simply, a reduction in the size of their stomachs — had a 32...
Jonathan GornallJuly 28, 202213 min
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It’s never too late for weight loss and doing so could save you from developing any one of 13 different cancers.
That’s the message of a remarkable new piece of research carried out by the world-renowned Cleveland Clinic in the US.
In a study involving over 30,000 patients, researchers found that obese adults who lost weight thanks to bariatric surgery — put simply, a reduction in the size of their stomachs — had a 32 percent lower risk of developing cancer. What’s more, they had an incredible 48 percent lower risk of cancer-related death, compared with similarly obese adults who did not have the surgery.
There are several different types of bariatric surgery, which is also known as metabolic, or simply weight loss, surgery. Patients can have a band fitted around their stomachs, so they feel full after eating less food than normal, a gastric bypass, in which the top of the stomach is joined to the small intestine, preventing all the calories in the food they eat being absorbed, or a “sleeve gastrectomy”, in which a proportion of the stomach is surgically removed. The patients in the Cleveland trial underwent either gastric bypass or gastric sleeve operations, both of which gave similar results.
Jame Abraham, chairman of the Hematology and Medical Oncology Department at Cleveland Clinic, admits that “further research needs to be done to understand the underlying mechanisms responsible for reduced cancer risk following bariatric surgery”.
But there is no arguing with the conclusion of the paper published in June 2022 in the Journal of the American Medical Association that, “given the growing epidemic of obesity worldwide, these findings have considerable public health implications.”
And not just for patients considered candidates for bariatric surgery.
According to the latest figures from the World Health Organisation, globally an estimated 1 billion people are obese, including 340 million adolescents and 39 million children.
The problem is particularly bad in the Middle East. Research published in the Journal of Obesity in February this year analyzed 101 studies involving 698,905 patients in 17 countries in the region, including the UAE and Saudi Arabia.
It found that the prevalence of obesity among adults across the Middle East was over 21 percent — highest in Syria (40 percent) and lowest in Yemen (8.8 percent). Overall, significantly more women than men tended to be obese. The proportion of obese adults in the UAE and Saudi Arabia respectively was 23 percent and 25 percent — about twice the global average. The World Health Organisation estimates that 13 percent of the world’s adult population (11 percent of men and 15 percent of women) are obese.
In short, says the WHO, “the issue has grown to epidemic proportions, with over 4 million people dying each year as a result of being overweight or obese”.
Obesity is bad for us in so many ways — it affects the heart, liver, kidneys,  joints, and reproductive system, and can cause diseases including type 2 diabetes, cardiovascular disease, hypertension and stroke. So much is obvious. But the other, largely unacknowledged health cost of obesity is cancer.
The link between obesity and cancer has been very well established by decades of research involving millions of people, and the mechanism is well understood. Excess fat cells create inflammation in the body, which in itself can trigger cancer. But these cells also cause the production of additional hormones and “growth factors” — proteins that stimulate cell production.
New cells are generated by a process called mitosis, in which a single cell divides into two identical cells. It’s when mitosis misfires that certain cancers can be created and, with a higher rate of cell division and reproduction in people who are obese, the odds of the process throwing up cancerous cells increases dramatically. Obesity has been linked to at least 13 different types of cancer, including two of the most common types — breast and bowel — and three of the hardest to treat: pancreatic, esophageal and gallbladder. Between them, in the US these account for 40 percent of all cancers diagnosed every year.

The Cleveland Clinic study looked at a group of 5,053 adult patients with obesity who had bariatric surgery between 2004 and 2017, and compared their outcomes to a control group of 25,265 obese patients who did not have surgery. The average age of all 30, 318 patients in the study, three-quarters of whom were women, was 46.

Bariatric surgery is a major surgical procedure, which should not be undertaken lightly and is considered a last resort, and only for patients who are extremely obese and have tried and failed to lose weight in more conventional ways, such as through exercise and amending their diet.

One rough guide to whether or not you have healthy body weight is a measurement known as BMI – Body Mass Index. It’s a simple calculation, based on weight, height and gender, and is somewhat crude. For example, it takes no account of how much muscle weight someone might be carrying, as opposed to fat.

Nevertheless, it is the one that is used in most healthcare systems to determine whether a patient qualifies for bariatric surgery. There are plenty of online calculators that will give you your BMI. Whichever one you use, on the BMI scale a “normal” weight is considered to be anything between 18.5 and 24.9, overweight is between 25 and 29.9, and obesity kicks in with a BMI of 30 or more.

In the UK, for example, a patient of the National Health Service has to have a BMI above 40 to be considered for bariatric surgery, and then only if they have tried every other way of losing weight, and are considered fit enough to be anesthetized and undergo surgery.
In the Cleveland clinic study, all the patients who were operated on had an average BMI of 45. Over 10 years, there was a remarkable difference in weight loss between the two groups. Those who were operated on had an average weight loss of 24.8kg more than the others. Furthermore, after 10 years 146 patients in the bariatric surgery group (2.9 percent) had developed an obesity-associated cancer, compared with 1,237 (4.9 percent) in the non-surgical group.

At the same time, 40 patients in the surgery group (0.8 percent) and 353 (1.4 percent) in the non-surgical group died from cancer, leading to the conclusion that, among obese patients, over a decade bariatric surgery is associated with a 48 percent lower risk of dying from cancer.

In other words, as the authors concluded, the study found that “among adults with obesity, bariatric surgery compared with no surgery was associated with a significantly lower incidence of obesity-associated cancer and cancer-related mortality”.
Good news, then, for obese patients who are offered bariatric surgery.
But the underlying message of the trial is one that everyone, wherever they fall on the BMI scale, should hear loud and clear: if you are obese, weight loss is a clear path to butting your risk of disease.
“Obesity is second only to tobacco as a preventable cause of cancer in the United States,” said the study’s senior author, Dr Steven Nissan, chief academic officer of Cleveland Clinic’s Heart, Vascular and Thoracic Institute. “This study provides the best possible evidence on the value of intentional weight loss to reduce cancer risk and mortality.”

Jonathan Gornall

Jonathan Gornall is a freelance British journalist who has lived and worked in the Middle East and is now based in the UK.

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