Scientists know that obesity is an established risk factor for cancer. Now, researchers find that excess weight in the waistline and hips is as much of a predictor of the disease as body mass index (BMI), a measurement denoting the ratio of weight to height.

Both BMI and where body fat is carried on the body can be good indicators of obesity-related cancer risk.- Heinz Freisling, International Agency for Research on Cancer

The author of the new study said an elevated risk of certain cancers and diabetes starts with a waist measurement of 40 inches for men and 35 inches for women. Why is this so?

Excess body fat elevates insulin levels, promotes inflammation and alters sex hormones like estrogen and progesterone, all of which are factors that have been linked to a heightened likelihood of cancer.

Moreover, according to the M.D. Anderson Center at the University of Texas, extra pounds in the belly indicate that fat is accumulating around and damaging some important organs. Increased fat in this area signals the body to manufacture more insulin, which can eventually lead to cancer, they explained.

In the study, researchers followed health data on 43,000 participants for 12 years. During this time, more than 1,600 people were diagnosed with obesity-related cancer. A correlation of waistline size with cancer diagnoses associated a gain of four inches to the waistline with a 13-percent rise in obesity-related cancer risk. In addition, it linked a gain of three inches to the hips with a 15-percent rise in colon cancer likelihood.

“Our findings show that both BMI and where body fat is carried on the body can be good indicators of obesity-related cancer risk. Specifically, fat carried around the waist may be important for certain cancers, but requires further investigation,” said Heinz Freisling, lead study author and scientist at the International Agency for Research on Cancer.

“To better reflect the underlying biology at play, we think it’s important to study more than just BMI when looking at cancer risk. And our research adds further understanding to how people’s body shape could increase their risk.”

After smoking, obesity is the biggest preventable cause of cancer. It’s associated with 13 types of malignancy; namely, colorectal; kidney; esophagus; breast; uterine; pancreas, liver; gall bladder; ovarian; thyroid; gastric cardia, the part of the stomach nearest to the esophagus; multiple myeloma, a blood cancer; and meningioma, a type of brain tumor.

“This study further highlights that however you measure it being overweight or obese can increase the risk of developing certain cancers, including breast and bowel,” said Julie Sharp, Cancer Research UK’s head of health information.

“It’s important that people are informed about ways to reduce their risk of cancer. And while there are no guarantees against the disease, keeping a healthy weight can help you stack the odds in your favour and has lots of other benefits too. Making small changes in eating, drinking and keeping physically active that you can stick with in the long term can help you get to a healthy weight — and stay there.”

The study was published in the British Journal of Cancer.

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