The association between obesity and colorectal adenoma: systematic review and meta-analysis

Objective. Obesity (body mass index [BMI] >= 30) or overweight (25 <= BMI <= 29.9) has been reported to be a risk factor for colorectal adenoma (CRA). However, this association remains controversial. The aim of this study was to determine the association between overweight or obesity and CRA. Design. Systematic review and meta-analysis were conducted using English language studies from EMBASE and MEDLINE. Appropriate observational studies were selected from 1966 through September 2011. Adjusted odds ratios (ORs) were extracted from each study. Results. One hundred and seventy full-text articles were reviewed after retrieving 1199 initial search results. Five studies in which BMI was treated as continuous variable, three studies in which BMI was dichotomized using a cutoff value of 25, three studies in which BMI was categorized into three groups using values of 22 and 25, and eight studies in which BMI was categorized into three groups using values of 25 and 30 were selected. Regarding risk for CRA, pooled OR [95% CI] of one increment increase in BMI was 1.02 [0.99-1.03] (random effects model [REM]), while that of BMI 25 was 1.27 [1.15-1.4] (Fixed effects model). Pooled ORs [95% CI] of BMI >= 22 and BMI >= 25 was 1.42 [0.69-2.9] [REM] and 1.81 [0.36-9.1] [REM], respectively. Pooled ORs [95% CI] of BMI >= 25 and BMI >= 30 was 1.16 [0.98-1.38] [REM] and 1.47 [1.18-1.83] [REM], respectively. Conclusion. Obesity and overweight are significant risk factors for CRA. However, there are no data showing linear relationship between increasing BMI and CRA.