Being overweight can raise the likelihood of being diagnosed with cancers of the stomach and digestive tract, as well as certain brain and reproductive tumours, international researchers said.
Limiting weight gain
A report in the New England Journal of Medicine adds eight more kinds of cancer to the list of those already known to be more likely among overweight people.
In 2002, the World Health Organisation's International Agency for Research on Cancer (IARC), based in France, said excess pounds could raise the risk of colon, oesophagus, kidney, breast and uterine cancer.
Now, it has added stomach, liver, gall bladder, pancreas, ovary and thyroid cancers, as well as a type of brain tumour known as meningioma and the blood cancer multiple myeloma, the report said.
Read: Obesity linked to ovarian cancer
Researchers reviewed more than 1,000 studies of excess weight and cancer risks, saying that limiting weight gain over decades can help to reduce the risk of those cancers.
"The burden of cancer due to being overweight or obese is more extensive than what has been assumed," said IARC Working Group chair Graham Colditz of the Washington University School of Medicine in St. Louis.
"Many of the newly identified cancers linked to excess weight haven't been on people's radar screens as having a weight component."
Cancer often arises with no explanation. Its causes can include viruses, pollutants, genetic factors and radiation.
Read: Obesity linked to two types of cancer
Certain lifestyle factors such as smoking and being overweight can also make a person more likely to get cancer.
Around nine percent of cancers among women in North America, Europe and the Middle East are believed to be linked to obesity, the report said.
Another wake-up call
Extra fat can promote inflammation and lead to an overproduction of oestrogen, testosterone and insulin – all of which can drive cancer growth, the study added.
Some 640 million adults and 110 million children around the world are obese.
"Lifestyle factors such as eating a healthy diet, maintaining a healthy weight and exercising, in addition to not smoking, can have a significant impact on reducing cancer risk," Colditz said.
"This is another wake-up call. It's time to take our health and our diets seriously."
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