Increased risk of 11 types of cancer linked to being overweight

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Increased risk of 11 types of cancer linked to being overweight, researchers warn

Nicola Davis
@NicolaKSDavis
Tuesday 28 February 2017 18.30 EST

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The new study by an international team adds weight to the warning, revealing that there is currently strong evidence for a link between excess body fat and an increased risk of 11 cancers: colon, rectum, endometrium, breast, ovary, kidney, pancreas, gastric cardia, biliary tract system and certain cancers of the oesophagus and bone marrow.

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While the new study does not shed light on how excess body weight is linked to an increased risk of various cancers, a number of explanations have previously been proposed. “We know that if you are overweight it causes lots of disruption of hormonal and metabolic pathways,” said Gunter, noting that excess fat has been linked to higher oestrogen levels, higher insulin levels and increased inflammation – all of which can affect cell division.


Being overweight, Orritt adds, is second only to smoking as the biggest preventable cause of cancer. “Whether it’s taking the stairs or switching to sugar-free versions of your favourite drinks, small changes can make a real difference, helping you keep a healthy weight and reducing your risk of cancer,” she said.

Dr Alison Tedstone, chief nutritionist at Public Health England, added that awareness was key. “Less than half the population realise that being obese increases the risk of cancer and, with almost two-thirds of adults carrying excess weight, this is worrying,” she said.

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How might obesity increase the risk of cancer?
Several possible mechanisms have been suggested to explain how obesity might increase the risks of some cancers.

Obese people often have chronic low-level inflammation, which can, over time, cause DNA damage that leads to cancer. Overweight and obese individuals are more likely than normal-weight individuals to have conditions or disorders that are linked to or that cause chronic local inflammation and that are risk factors for certain cancers (26). For example, chronic local inflammation induced by gastroesophageal reflux disease or Barrett esophagus is a likely cause of esophageal adenocarcinoma. Obesity is a risk factor for gallstones, a condition characterized by chronic gallbladder inflammation, and a history of gallstones is a strong risk factor for gallbladder cancer (27). Chronic ulcerative colitis (a chronic inflammatory condition) and hepatitis (a disease of the liver causing inflammation) are risk factors for different types of liver cancer (28).

Fat tissue (also called adipose tissue) produces excess amounts of estrogen, high levels of which have been associated with increased risks of breast, endometrial, ovarian, and some other cancers.

Obese people often have increased blood levels of insulin and insulin-like growth factor-1 (IGF-1). (This condition, known as hyperinsulinemia or insulin resistance, precedes the development of type 2 diabetes.) High levels of insulin and IGF-1 may promote the development of colon, kidney, prostate, and endometrial cancers (29).

Fat cells produce adipokines, hormones that may stimulate or inhibit cell growth. For example, the level of an adipokine called leptin, which seems to promote cell proliferation, in the blood increases with increasing body fat. And another adipokine, adiponectin—which is less abundant in obese people than in those of normal weight—may have antiproliferative effects.

Fat cells may also have direct and indirect effects on other cell growth regulators, including mammalian target of rapamycin (mTOR) and AMP-activated protein kinase.

Other possible mechanisms by which obesity could affect cancer risk include changes in the mechanical properties of the scaffolding that surrounds breast cells (30) and altered immune responses, effects on the nuclear factor kappa beta system, and oxidative stress (31).

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