International Agency for Research on Cancer (IARC) and World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) classify the role of this risk factor in cancer development.[1,2] 11% of bowel cancer cases in the UK are caused by overweight and obesity.[3]

Body-mass index (BMI)

Colon cancer risk is 30% higher in men per 5-unit body mass index (BMI) increase, an umbrella study of meta-analyses showed.[4] Colon cancer risk is 12% higher in women per 5-unit body mass index (BMI) increase, an umbrella study of meta-analyses showed.[4] the association in obese women may be stronger in premenopausal than postmenopausal women.[5]

Rectal cancer risk is 9% higher in men per 5-unit body mass index (BMI) increase, an umbrella study of meta-analyses showed.[4] There is no association between BMI and rectal cancer in women.[4]

Bowel cancer risk among men is 10% higher per 5 kg gained during adulthood, a meta-analysis showed.[6] Bowel cancer risk among women is not associated with weight gain during adulthood.[6]

Bowel adenoma risk is 47% higher in people who are obese by BMI compared with those who are healthy-weight, a meta-analysis showed.[7]

Waist circumference

Colon cancer risk is 25% higher in people per 10cm increase in waist circumference, an umbrella study of meta-analyses showed.[4]

Bowel cancer risk is 46% higher in people with the largest waist circumference, versus those with the smallest, a meta-analysis showed.[8]

Bowel adenoma risk is 39% higher in people with the largest waist circumference, versus those with the smallest, a meta-analysis showed.[9]

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