title: The effect of body weight reduction on the incidence of colorectal adenoma.
abstract: OBJECTIVE
  Obesity is thought to be associated with colorectal cancer and adenoma. We aimed to investigate the effect of body weight on the risk of colorectal adenoma both in cross-sectional and longitudinal analyses.
  
  
  METHODS
  This is a retrospective cohort study in a large-scale health appraisal institution in Japan. A total of 7,963 asymptomatic, average-risk Japanese were enrolled at initial examinations, and 2,568 subjects who underwent a second colonoscopy after 1 yr were investigated. The association with the prevalence of colorectal adenoma was evaluated according to the body mass index (BMI) at the initial examination. The incidence of colorectal adenoma at the second colonoscopy was investigated according to the initial BMI and body weight changes during the year.
  
  
  RESULTS
  The prevalence of colorectal adenoma increased in relation to increases in the BMI: 15.4%, 20.6%, 22.7%, and 24.2%, respectively, in the first (BMI < 21.350), second (21.350 < or = BMI < 23.199), third (23.199 < or = BMI < 25.156), and fourth (25.156 < or = BMI) quartiles. The adjusted odds ratios in reference to Group Q1 were 1.15 (95% CI 0.97-1.37, P= 0.1) for Group Q2, 1.19 (1.01-1.41, P= 0.04) for Group Q3, and 1.32 (1.12-1.56, P= 0.001) for Group Q4. The incidence rates of colorectal adenoma after 1 yr also increased proportionally according to the initial BMI: Group Q1 (12.9%), Group Q2 (15.7%), Group Q3 (18.3%), and Group Q4 (19.0%).
  
  
  CONCLUSIONS
  Obesity was associated with the risk for colorectal adenoma, and body weight reduction was suggested to decrease this risk.
authors.affiliation: Department of Gastroenterology, University of Tokyo, Tokyo, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yamaji
authors.forename: Makoto
authors.initials: M
authors.lastname: Okamoto
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Yoshida
authors.forename: Takao
authors.initials: T
authors.lastname: Kawabe
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Wada
authors.forename: Toru
authors.initials: T
authors.lastname: Mitsushima
authors.forename: Masao
authors.initials: M
authors.lastname: Omata
mesh_terms: D000236:Adenoma / Q000453:epidemiology*; D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000473:pathology; D015995:Prevalence; D012189:Retrospective Studies; D015431:Weight Loss