Body mass index and oxidative DNA damage: a longitudinal study.

Leanness has been shown to be related to an increased risk of some cancer forms, including lung cancer. However, biological evidence supporting a causal link between leanness and carcinogenesis is limited. The authors investigated longitudinally the association between body mass index (BMI) and levels of urinary 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative DNA damage, using data from 174 healthy employees who participated in a lifestyle intervention study. 8-OHdG levels were measured using automated high-performance liquid chromatography and adjusted for urinary creatinine levels. Analysis of repeated measurements using a random effects model detected a statistically significant inverse association between BMI and 8-OHdG levels (P = 0.003); one unit decrease in BMI was associated with a 2.7% (95% confidence interval 0.9-4.4) increase in 8-OHdG levels. The association was pronounced among men consuming less than 20 cigarettes per day (8.8% increase per unit decrease in BMI) and among non-smoking men (3.7% increase). The results based on a longitudinal observation suggest that weight loss is associated with increased oxidative DNA damage, a state presumably related to an increased risk of cancer.