Obesity linked to colorectal adenoma risk

A meta-analysis has shown that increasing adiposity shows a direct relationship with the development of adenomas in the colon- helping to shed light on the link between obesity and colorectal cancer (CRC).

Individuals with a body mass index (BMI) of 25 kg/m² or more had a 24% greater risk for colorectal adenomas than those with a BMI below 25 kg/m².

Furthermore, comparison of BMI categories showed a clear dose-response relationship between increasing obesity and adenoma risk. The odds ratio (OR) for patients with a BMI between 25 and 30 kg/m² was 1.21, while for those with a BMI greater than 30 kg/m², the OR was 1.33. However, obesity had no significant influence on the relative risk for adenoma progression.

"An increased understanding between the development of colorectal adenomas and BMI categories can clarify the mechanistic steps linking adiposity and CRC and may be useful in determining the benefits of early CRC screening," say Thanos Athanasiou (Imperial College London, UK) and colleagues.

The meta-analysis pooled data from 23 studies, including 105,190 participants, 42,179 of whom had a BMI of 25 kg/m² or above, denoting overweight or obesity.

As well as finding associations with obesity, the results also indicated that active smoking might also increase colorectal adenoma prevalence. The researchers also found a significant association between female gender (but not male gender) and colorectal adenoma formation according to BMI. Premenopausal women had a higher risk for adenomas compared with postmenopausal women, suggesting a potential role of endogenous estrogens in colorectal adenoma formation.

The review, published in the American Journal of Gastroenterology, adds to growing epidemiologic and meta-analysis evidence of a link between obesity and CRC. "Further identification of the tumorigenic effects of adiposity in cancer progression," the authors hope, "may lead to novel interventions in cancer management."

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