EU study finds link between middle-aged spread and colon cancer

Brussels, 03 Aug 2006

Men and women who have larger waistlines may be at an increased risk of colon cancer, according to the findings of an EU-funded study.

Over a six-year period, researchers in the 'European Prospective Investigation into Cancer, Chronic Diseases, Nutrition and Lifestyle' (EPIC) project monitored a total of 495,417 cancer-free men and women aged between 25 and 70, who were recruited across 10 European countries. Participants' weight, height and body mass (BMI-body weight divided by body height) were measured. They were also asked to complete questionnaires on diet, exercise and other lifestyle factors.

During follow-up, 984 participants were diagnosed with colon cancer, while 586 were diagnosed with rectum cancer. Researchers found that in both sexes, the waist circumference was positively related to the risk of colon cancer. Women with a waist to hip ratio (WHR) over 0.85 had a 52 per cent higher risk of colon cancer than those with a WHR under 0.73. Similar values were observed in men, whose colon cancer risk increased by 51 per cent from those with the lowest WHR (<0.89).

The findings, which were published in the Journal of the National Cancer Institute, also showed that men and women who were taller were at a greater risk of colon cancer risk. One possible reason for this is the higher number of cells: the higher the number of cells present, the higher the probability of cell mutations. In addition, taller individuals probably have a relatively high exposure to growth-regulating hormones (growth hormone, insulin-like growth factors and insulin), which, in turn, are associated with cancer development.

In addition to these commonalities, some sex specific differences were observed on body weight. The study found that men with overall larger body mass (BMI) were more at risk than women. Men with a BMI over 29.4 had a 55 per cent higher risk of colon cancer than slim men, with a BMI under 23.6. In women, the risk increased by only six per cent.

One potential reason, suggested by the study, for this discrepancy is that men and women have different body compositions. Fat makes up a lower percentage of the body mass of men (approximately 20 per cent) than of women (approximately 30 per cent). The relationship of body weight to fat distribution also differs between men and women. Higher body weight is more closely related to abdominal obesity than lower body obesity in men and more closely related to gluteofemoral obesity than to abdominal obesity in women. Furthermore, upper-body fat has been shown to be more strongly associated with metabolic abnormalities than lower-body obesity.

'Our results support the hypothesis that abdominal body fat is especially important for development of colon cancer. This agrees with our observation that BMI is rather inappropriate for predicting colon cancer in women because the relation between BMI and waist circumference is not as close as in men. This is probably because men gain weight primarily by increasing abdominal body fat, whereas in women, body fat normally also accumulates in other parts of the body,' says Heiner Boeing, head of EPIC at the German Institute of Human Nutrition in Potsdam-Rehbrücke (DIfE).

Other reasons for gender differences in the body weight-colon cancer relationship may be related to use of hormone replacement therapy (HRT) in postmenopausal women. The study found that the link between waist circumference and the risk of colon cancer was marginally higher among non-users than users of HRT.

Why increased abdominal fat raises the risk of colon cancer is currently unknown. The insulin resistance associated with abdominal obesity and the resulting increase in circulating insulin levels may possibly play a role. Other potential mediators are leptin and adiponectin. The EPIC project consortium will continue to examine these and other biomarkers for their possible link to colorectal cancer.

The findings give further credence to public health efforts aiming to reduce the prevalence of obesity. The author of this section of the study, Tobias Pischon, recommends that waist measurements should be included in any guidelines to maintain a healthful lifestyle for disease prevention.

Further information

CORDIS RTD-NEWS/© European Communities, 2006
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